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How Structural Modifications of Insulin Icodec Contributes to Its Prolonged Duration of Action: A Structural and Biophysical Perspective

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Wei Li  *

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15 November 2023

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16 November 2023

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Abstract
Insulin icodec of Novo Nordisk is a novel long-acting insulin analogue that exhibits an extended duration of action, providing a promising treatment option for individuals with diabetes. It has been reported that the incorporation of fatty acid moieties into insulin icodec plays a crucial role in its prolonged action, as these fatty acid chains facilitate the formation of stable hexameric structures, thereby delaying insulin absorption and promoting sustained release. Yet, the underlying biophysics still is elusive of the roles of the three site-specific mutations (Y14A\_E, Y37B\_H, F46B\_H) of insulin icodec in its prolonged activity. Thus, through a comprehensive structural and biophysical analysis of the insulin (both native and icodec) structures bound to its receptor, this article delves deep into the biophysics underlying the molecular design of insulin icodec, and identified a delicate biophysical mechanism through which two missense mutations of insulin icodec (Y37B\_H and F46B\_H) contribute to its prolonged duration of action. Overall, this structural and biophysical investigation provides valuable insights into the mechanisms underlying the relationship between three site-specific mutations and prolonged duration of action of insulin icodec, while understanding these modifications at a structural and biophysical level can aid in the rational design of future long-acting insulin analogues, offering further enhanced therapeutic options for diabetic patients.
Keywords: 
Subject: Biology and Life Sciences  -   Biophysics

1. Introduction

Ligand-receptor binding affinity is an essential parameter in both computational and experimental drug discovery & design [1]. Thanks to the continued development of experimental structural biology and the fifty-three-year old Protein Data Bank (PDB) [2,3], a high-throughput comprehensive structural biophysical analysis becomes possible [4] for specific ligand-receptor complex structures deposited in PDB, such that our understanding of the structural and biophysical basis of their interfacial stability is able to help us modify the binding affinity of certain drug target and its interacting partners.
Take insulin icodec for example [5,6,7,8]. Insulin icodec of Novo Nordisk is a long-acting insulin analogue for better management of blood sugar levels in people with diabetes [9,10,11]. Insulin icodec is designed to provide a steady release of insulin throughout the day, mimicking the natural insulin production in the body [12,13,14]. Insulin icodec is typically administered through injection once a week, which helps lower blood sugar levels by allowing glucose to enter the body’s cells, where it is subsequently used for energy production [15,16]. Moreover, insulin icodec has a distinct pharmacokinetic profile compared to other long-acting insulin analogs. It exhibits a long duration of action, with a half-life of approximately 196 hours, leading to improved glycemic control and reduced hypoglycemia risk [17,18]. Interestingly, Icosema (of Novo Nordisk, too) [19,20,21,22] represents a combination medication that consists of insulin icodec and semaglutide, which belongs to a class of medications called glucagon-like peptide-1 (GLP-1) receptor agonists and helps regulate blood sugar levels by stimulating the release of insulin, reducing the production of glucagon (a hormone that increases blood sugar levels), and slowing down the digestion process for weight reduction [23,24,25].
Given the two-dimensional structures of native human insulin and insulin icodec as shown in Figure 1, this article summarizes below a list of structural modifications of insulin icodec compared to native human insulin [26,27,28]:
Overall, these structural modifications (Figure 2) in insulin icodec result in a more stable and longer-acting insulin analogue compared to regular insulin, providing a more consistent and sustained blood glucose-lowering effect:
  • insulin icodec is able to form aggregates or clusters at the subcutaneous injection site, gradually releasing into the bloodstream over an extended period.
  • insulin icodec undergoes structural modifications that increases its stability and solubility and preventing enzyme-mediated degradation and rapid clearance [36].
  • insulin icodec is conjugated with a fatty acid at position B30 (K50B_C20, Figure 2). After injection, the fatty acid chain in insulin icodec interacts with albumin in the subcutaneous tissue, forming reversible albumin-insulin complexes. These complexes act as a reservoir, gradually releasing insulin icodec into the bloodstream, increasing its fat solubility and allowing it to bind to fatty acid-binding proteins, forming a depot of the insulin icodec reversibly bound to albumin.
  • the incorporation of fatty acid chains facilitate the formation of stable hexameric structures, thereby delaying insulin absorption and promoting sustained release.
With respect to the addition of a fatty acid (K50B_C20, Figure 2), it is conceivable that the deletion of threonine at position B30 (T51B_del, Figure 2) is for K50B_C20 to take place easier and more efficiently than without the deletion of threonine at position B30. Nonetheless, the underlying biophysics remains elusive of the roles of the three site-specific mutations (Y14A_E, Y37B_H, F46B_H) of insulin icodec in its prolonged activity. Therefore, through a comprehensive structural and biophysical analysis of the insulin (both native and icodec) structures bound to its receptor, this article delves deep into the biophysics underlying the molecular design of insulin icodec, and identified a delicate biophysical mechanism through which two missense mutations of insulin icodec (Y37B_H and F46B_H) contribute to its prolonged duration of action.

2. Materials and Methods

2.1. A summary of insulin receptor-related structures in PDB

As listed in Table 1, as of November 16, 2023, there are a variety of experimental complex structures of insulin (analogues) bound to its receptor (IR), such as PDB entries 7PG3 (insulin receptor bound to 3 insulins), 7PG4 (insulin receptor bound to 2 insulins), 6SOF (insulin receptor bound to 4 insulins).
Among the insulin receptor-related structures listed in Table 1, PDB entry 6SOF [37] is the only experimental complex structure of insulin bound to IR, where all four distinct binding sites of the IR dimer are saturated by four insulin molecules. Therefore, PDB entry 6SOF [37] is chosen here as the structural template for subsequent structural modelling of insulin icodec bound to IR.

2.2. Construction of a complex structural model of insulin icodec bound to IR

Towards the construction of a complex structural model of insulin icodec bound to IR, first, the amino acid sequences of the two chains of native human insulin and IR (according to PDB entry 6SOF [37], supplementary file nati.pdb) are listed in italics in fasta format as below,
>InsulinA
GIVEQCCTSICSLYQLENYCN
>InsulinB
FVNQHLCGSHLVEALYLVCGERGFFYTPKT
>IRpartOne
HLYPGEVCPGMDIRNNLTRLHELENCSVIEGHLQILLMFKTRPEDFRDLSFPKLIMITDYLLLFRVYGLESLKDLFPNLTVIRGSRLFFNYALVIFEMVHLKELGLYNLMNITRGSVRIEKNNELCYLATIDWSRILDSVEDNYIVLNKDDNEECGDICPGTAKGKTNCPATVINGQFVERCWTHSHCQKVCPTICKSHGCTAEGLCCHSECLGNCSQPDDPTKCVACRNFYLDGRCVETCPPPYYHFQDWRCVNFSFCQDLHHKCKNSRRQGCHQYVIHNNKCIPECPSGYTMNSSNLLCTPCLGPCPKVCHLLEGEKTIDSVTSAQELRGCTVINGSLIINIRGGNNLAAELEANLGLIEEISGYLKIRRSYALVSLSFFRKLRLIRGETLEIGNYSFYALDNQNLRQLWDWSKHNLTITQGKLFFHYNPKLCLSEIHKMEEVSGTKGRQERNDIALKTNGDQASCENELLKFSYIRTSFDKILLRWEPYWPPDFRDLLGFMLFYKEAPYQNVTEFDGQDACGSNSWTVVDIDPPLRSNDPKSQNHPGWLMRGLKPWTQYAIFVKTLVTFSDERRTYGAKSDIIYVQTDATNPSVPLDPISVSNSSSQIILKWKPPSDPNGNITHYLVFWERQAEDSELFELDYCLKGLKLPSRTWSPPFESEDSQKHNQSEYEDSAGECCSCPKTDSQILKELEESSFRKTFEDYLHNVVFVPRPS
>IRpartTwo
HRPFEKVVNKESLVISGLRHFTGYRIELQACNQDTPEERCSVAAYVSARTMPEAKADDIVGPVTHEIFENNVVHLMWQEPKEPNGLIVLYEVSYRRYGDEELHLCVSRKHFALERGCRLRGLSPGNYSVRIRATSLAGNGSWTEPTYFYVTDYLDVPSNIAK
Second, the amino acid sequences of the two chains of insulin icodec and IR are listed in italics in fasta format as below,
>InsulinIcodecA
GIVEQCCTSICSLEQLENYCN
>InsulinIcodecB
FVNQHLCGSHLVEALHLVCGERGFFHTPKT
>IRpartOne
HLYPGEVCPGMDIRNNLTRLHELENCSVIEGHLQILLMFKTRPEDFRDLSFPKLIMITDYLLLFRVYGLESLKDLFPNLTVIRGSRLFFNYALVIFEMVHLKELGLYNLMNITRGSVRIEKNNELCYLATIDWSRILDSVEDNYIVLNKDDNEECGDICPGTAKGKTNCPATVINGQFVERCWTHSHCQKVCPTICKSHGCTAEGLCCHSECLGNCSQPDDPTKCVACRNFYLDGRCVETCPPPYYHFQDWRCVNFSFCQDLHHKCKNSRRQGCHQYVIHNNKCIPECPSGYTMNSSNLLCTPCLGPCPKVCHLLEGEKTIDSVTSAQELRGCTVINGSLIINIRGGNNLAAELEANLGLIEEISGYLKIRRSYALVSLSFFRKLRLIRGETLEIGNYSFYALDNQNLRQLWDWSKHNLTITQGKLFFHYNPKLCLSEIHKMEEVSGTKGRQERNDIALKTNGDQASCENELLKFSYIRTSFDKILLRWEPYWPPDFRDLLGFMLFYKEAPYQNVTEFDGQDACGSNSWTVVDIDPPLRSNDPKSQNHPGWLMRGLKPWTQYAIFVKTLVTFSDERRTYGAKSDIIYVQTDATNPSVPLDPISVSNSSSQIILKWKPPSDPNGNITHYLVFWERQAEDSELFELDYCLKGLKLPSRTWSPPFESEDSQKHNQSEYEDSAGECCSCPKTDSQILKELEESSFRKTFEDYLHNVVFVPRPS
>IRpartTwo
HRPFEKVVNKESLVISGLRHFTGYRIELQACNQDTPEERCSVAAYVSARTMPEAKADDIVGPVTHEIFENNVVHLMWQEPKEPNGLIVLYEVSYRRYGDEELHLCVSRKHFALERGCRLRGLSPGNYSVRIRATSLAGNGSWTEPTYFYVTDYLDVPSNIAK
Lastly, to build a reliable structural model of the insulin icodec bound to IR, the amino acid sequences above (>InsulinIcodecA, >InsulinIcodecB, >IRpartOne and >IRpartTwo) were plugged into the SWISS-MODEL homology modeling server [38,39] and the Modeller software [40] to build a homology structural model with reasonable accuracy, supplementary file icod.pdb, which was subsequently subject to a set of comprehensive structural biophysical analysis as described previously in [4].

2.3. A comprehensive structural and biophysical analysis of insulin icodec bound to IR

As described previously in [4], a comprehensive structural and biophysical analysis was conducted for the structural model of the insulin icodec bound to IR (supplementary file icod.pdb). Specifically, the salt bridge analysis was conducted with an in-house python script only for titrateable residues (Asp, Glu, Lys, Arg and His), 4.0 Å was used as the cutoff distance for the two oppositely charged groups [4]. The hydrogen bond analysis was also conducted for only side chain nuclei with an in-house python script, and employed two geometric criteria: (a) a cutoff value of the angle formed by acceptor (A), donor (D) and hydrogen (H) ( ∠ A D H ) of 30°; (b) a cutoff value of donor-acceptor distance at 3.0 Å. That is, a hydrogen bond is only considered to be formed if ∠ A D H is no larger than 30° and the donor-acceptor distance is not larger than 3.0 Å [4].

3. Results

As described above, the addition of a fatty acid to insulin icodec (K50B_C20, Figure 2) is for it to interact with albumin and form reversible albumin-insulin complexes, i.e., a reservoir for gradually releasing insulin icodec into the bloodstream. Moreover, it is highly likely that the deletion of threonine at position B30 (T51B_del, Figure 2) is for K50B_C20 to take place easier and more efficiently. As a result, the comprehensive structural and biophysical analysis here focuses on the three site-specific mutations (Y14A_E, Y37B_H, F46B_H) of insulin icodec.
Coincidentally, the three mutations (Y14A_E, Y37B_H, F46B_H) invariably fall into the same category of the substitution of an amino acid residue with an amino acid residue with a hydrophilic side chain. Briefly, with a set of comprehensive structural and biophysical analysis [4] for supplementary files icod.pdb and nati.pdb, this article here for the first time reports that
  • Y14A_E (Figure 1 and Figure 2) is not involved in any salt bridge or hydrogen bond within insulin icodec itself.
  • Y14A_E (Figure 1 and Figure 2) is not involved in any salt bridge or hydrogen bond at the binding interface between insulin icodec and IR.
  • Y37B_H (Figure 1 and Figure 2) is involved in one salt bridge within insulin icodec itself (Figure 3, Table 2 and Table 4).
  • Y37B_H (Figure 1 and Figure 2) is not involved in any hydrogen bond within insulin icodec itself.
  • Y37B_H (Figure 1 and Figure 2) is not involved in any salt bridge or hydrogen bond at the binding interface between insulin icodec and IR.
  • F46B_H (Figure 1 and Figure 2) is not involved in any salt bridge or hydrogen bond within insulin icodec itself.
  • F46B_H (Figure 1 and Figure 2) is not involved in any salt bridge or hydrogen bond at the binding interface between insulin icodec and IR.
Of the three mutations (Y14A_E, Y37B_H, F46B_H), a total of three electrostatic interactions (including salt bridges and hydrogen bond) were identified and listed as below in Table 2.
Specifically, before Y37B_H (Figure 1 and Figure 2), i.e., in the case of native human insulin (Table 3), only one salt bridge (3.204 Å long) was formed between C_LYS_921 (of IR) and F_GLU_1804 (of regular insulin) at the binding interface of native human insulin bound to IR (supplementary file nati.pdb). Similarly, after Y37B_H (Figure 1 and Figure 2), i.e., in the case of insulin icodec (Table 4), only one salt bridge (3.669 Å long) was formed between C_LYS_921 (of IR) and F_GLU_1804 (of insulin icodec) at the binding interface of insulin icodec bound to IR (supplementary file icod.pdb). Interestingly, apart from the interfacial salt bridge between C_LYS_921 (of IR) and F_GLU_1804 (of insulin icodec), there is also one intra-molecular salt bridge (3.659 Å long) between F_HIS_1799 (of insulin icodec) and F_GLU_1804 (of insulin icodec).
Thus, it is obvious that in the case of native human insulin (Table 3), F_GLU_1804 (of regular insulin) focuses on binding to C_LYS_921 (of IR) alone with a 3.204 Å long interfacial salt bridge between regular insulin and IR, while in the case of insulin icodec (Table 4), F_GLU_1804 (of insulin icodec) has to bind both C_LYS_921 (of IR) and F_HIS_1799 (of insulin icodec) with two salt bridges, as listed in Table 4.
Furthermore, the existence of F_HIS_1799 (of insulin icodec) is entirely due to the site-directed mutation Y37B_H (Figure 1 and Figure 2). Therefore, it is entirely due to the site-directed mutation Y37B_H that the salt bridge at the binding interface between insulin and IR becomes weaker (from 3.204 Å long to 3.669 Å long), but is still not disrupted by the site-directed mutation Y37B_H, such that the binding affinity of ligand-receptor is lowered but not eliminated by the site-directed mutation Y37B_H (Figure 1 and Figure 2), and thereby ensuring downstream signal transduction for the prolonged blood glucose-lowering effect of insulin icodec.
With respect to the site-directed mutation F46B_H (Figure 1 and Figure 2), it is not involved in any salt bridge or hydrogen bond within insulin icodec itself, nor is it involved in any salt bridge or hydrogen bond at the binding interface between insulin icodec and IR, according comprehensive structural and biophysical analysis [4] of insulin icodec bound to IR (supplementary file icod.pdb). Nonetheless, a close inspection with PyMol [41] of supplementary file icod.pdb revealed that the positively charged side chain of His1808 of insulin icodec (due to the site-specific mutation F46B_H, Figure 2) is only 6.4 Å away (Figure 4) from the positively charged side chain of R900 (Arg900) of IR. Despite the cutoff distance (4.0 Å) as used in [4], a distance 6.4 Å is not sufficient to be defined as strong an electrostatic interaction as a salt bridge, it still is able to induce a weak electrostatic repulsive force between the positively charged side chains of His1808 of insulin icodec and that of R900 of IR, and thereby reducing the binding affinity between insulin icodec and IR. Moreover, in case the site-specific mutation is not F46B_H, Figure 2), but F46B_E, i.e., it is not a histidine, but a glutamate, it is conceivable that the distance between Glu1808 of insulin icodec and R900 of IR is shorter than 6.4 Å (Figure 4), make it highly likely for a novel stable salt bridge to be formed between E1808 (Glu1808) of insulin icodec and R900 (Arg900) of IR, according to the 4 Å distance cutoff as used in [4].
Finally, with respect to the site-directed mutation Y14A_E (Figure 1 and Figure 2), , it mutation does not seem to impact the binding between insulin icodec and IR, as it is a fully solvent-exposed amino acid residue, as shown by Figure 5. Thus, as of November 16, 2023 from structural and biophysical perspective, it is not clear yet why site-directed mutation Y14A_E is included in the design of insulin icodec. Here, this article is only able to speculate that Y14A_E is for the overall structural stability of icodec insulin for it to exert its prolonged blood glucose-lowering effect for patients with diabetes.

4. Conclusion and Discussion

For the first time, through a comprehensive structural and biophysical analysis of the insulin (both native and icodec) structures bound to its receptor, this article puts forward a delicate biophysical mechanism through which two missense mutations of insulin icodec (Y37B_H and F46B_H) contribute to its prolonged duration of action. In addition to the biophysics underlying the molecular design of insulin icodec, this article also argues that this structural and biophysical understanding is of help for rational design of future long-acting insulin analogues, offering further enhanced therapeutic options for diabetic patients.

5. Ethical statement

No ethical approval is required.

6. Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the author used OpenAI’s ChatGPT in order to improve the readability of the manuscript, and to make it as concise and short as possible. After using this tool, the author reviewed and edited the content as needed and takes full responsibility for the content of the publication.

Author Contributions

Conceptualization, W.L.; methodology, W.L.; software, W.L.; validation, W.L.; formal analysis, W.L.; investigation, W.L.; resources, W.L.; data duration, W.L.; writing–original draft preparation, W.L.; writing–review and editing, W.L.; visualization, W.L.; supervision, W.L.; project administration, W.L.; funding acquisition, not applicable.

Funding

This research received no external funding.

Conflicts of Interest

The author declares no conflict of interest.

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Figure 1. A brief illustration of the two-dimensional structures of native human insulin and insulin icodec of Novo Nordisk [29,30,31]. In this figure, the amino acid residues with pink backgrounds represents the positions of the three site-specific mutations (Y14A_E, Y37B_H, F46B_H) of insulin icodec.
Figure 1. A brief illustration of the two-dimensional structures of native human insulin and insulin icodec of Novo Nordisk [29,30,31]. In this figure, the amino acid residues with pink backgrounds represents the positions of the three site-specific mutations (Y14A_E, Y37B_H, F46B_H) of insulin icodec.
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Figure 2. A summary of the structural modification of insulin icodec in comparison to native human insulin. In this figure, Y14A_E (i.e., replacement of Tyr14 (Y14) at position A14 (position 14 of chain A) by a histidine), Y37B_H (i.e., replacement of Tyr16 (Y16) at position B16 by a histidine) and F46B_H (i.e., replacement of Phe25 (F25) at position B25 by a histidine) represent three site-specific missense mutations of insulin icodec, T51B_del represents deletion of Thr30 (T30) at position B30, while K50B_C20 represents the addition of a 20-carbon fatty acid to the lysine amino acid (K50B) at position B29 [32,33,34,35].
Figure 2. A summary of the structural modification of insulin icodec in comparison to native human insulin. In this figure, Y14A_E (i.e., replacement of Tyr14 (Y14) at position A14 (position 14 of chain A) by a histidine), Y37B_H (i.e., replacement of Tyr16 (Y16) at position B16 by a histidine) and F46B_H (i.e., replacement of Phe25 (F25) at position B25 by a histidine) represent three site-specific missense mutations of insulin icodec, T51B_del represents deletion of Thr30 (T30) at position B30, while K50B_C20 represents the addition of a 20-carbon fatty acid to the lysine amino acid (K50B) at position B29 [32,33,34,35].
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Figure 3. Glu1804 of insulin icodec forms two salt bridges, one with His1799 of insulin icodec (due to the Y37B_H substitution), and another one with Lys921 of IR at their binding interface. This figure is prepared by PyMol [41].
Figure 3. Glu1804 of insulin icodec forms two salt bridges, one with His1799 of insulin icodec (due to the Y37B_H substitution), and another one with Lys921 of IR at their binding interface. This figure is prepared by PyMol [41].
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Figure 4. A 6.4 Å long electrostatic repulsive force between between H1808 of insulin icodec (His1808, due to the site-specific mutation F46B_H, Figure 2) and R900 of IR. This figure is prepared by PyMol [41] according to supplementary file icod.pdb.
Figure 4. A 6.4 Å long electrostatic repulsive force between between H1808 of insulin icodec (His1808, due to the site-specific mutation F46B_H, Figure 2) and R900 of IR. This figure is prepared by PyMol [41] according to supplementary file icod.pdb.
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Figure 5. A fully solvent-exposed Glu14 of insulin icodec according to supplementary file icod.pdb. This figure is prepared by PyMol [41].
Figure 5. A fully solvent-exposed Glu14 of insulin icodec according to supplementary file icod.pdb. This figure is prepared by PyMol [41].
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Table 1. Experimentally determined IR-related structures (released newest from oldest) in the Protein Data Bank (PDB [2]) as of November 16, 2023, QUERY code: UniProt Molecule Name = "Insulin receptor".
Table 1. Experimentally determined IR-related structures (released newest from oldest) in the Protein Data Bank (PDB [2]) as of November 16, 2023, QUERY code: UniProt Molecule Name = "Insulin receptor".
PDB ID Structure Title (release date from newest to oldest)
8DWN Crystal structure of bis-phosphorylated insulin receptor kinase domain
7YQ3 human insulin receptor bound with A43 DNA aptamer and insulin
7YQ4 human insulin receptor bound with A62 DNA aptamer and insulin - locally refined
7YQ5 human insulin receptor bound with A62 DNA aptamer and insulin
7YQ6 human insulin receptor bound with A62 DNA aptamer
8EYX Cryo-EM structure of 4 insulins bound full-length mouse IR mutant with physically decoupled alpha CTs (C684S/C685S/C687S; denoted as IR-3CS) Asymmetric conformation 1
8EYY Cryo-EM structure of 4 insulins bound full-length mouse IR mutant with physically decoupled alpha CTs (C684S/C685S/C687S, denoted as IR-3CS) Asymmetric conformation 2
8EZ0 Cryo-EM structure of 4 insulins bound full-length mouse IR mutant with physically decoupled alpha CTs (C684S/C685S/C687S; denoted as IR-3CS) Symmetric conformation
8GUY human insulin receptor bound with two insulin molecules
7U6D Head region of insulin receptor ectodomain (A-isoform) bound to the non-insulin agonist IM459
7U6E Head region of insulin receptor ectodomain (A-isoform) bound to the non-insulin agonist IM462
7PHT Structure of Insulin receptor’s transmembrane domain
8DTL Cryo-EM structure of insulin receptor (IR) bound with S597 peptide
8DTM Cryo-EM structure of insulin receptor (IR) bound with S597 component 2
7S0Q Head region of a complex of IGF-I with the ectodomain of a hybrid insulin receptor / type 1 insulin-like growth factor receptor
7S8V Leg region of a complex of IGF-I with the ectodomain of a hybrid insulin receptor / type 1 insulin-like growth factor receptor
7SL1 Full-length insulin receptor bound with site 1 binding deficient mutant insulin (A-V3E)
7SL2 Full-length insulin receptor bound with site 2 binding deficient mutant insulin (A-L13R) – asymmetric conformation
7SL3 Full-length insulin receptor bound with site 2 binding deficient mutant insulin (A-L13R) – symmetric conformation
7SL4 Full-length insulin receptor bound with site 2 binding deficient mutant insulin (B-L17R) – asymmetric conformation
7SL6 Full-length insulin receptor bound with site 2 binding deficient mutant insulin (B-L17R) – symmetric conformation
7SL7 Full-length insulin receptor bound with both site 1 binding deficient mutant insulin (A-V3E) and site 2 binding deficient mutant insulin (A-L13R)
7STH Full-length insulin receptor bound with unsaturated insulin WT (2 insulin bound) symmetric conformation
7STI Full-length insulin receptor bound with unsaturated insulin WT (1 insulin bound) asymmetric conformation
7STJ Full-length insulin receptor bound with unsaturated insulin WT (2 insulins bound) asymmetric conformation (Conformation 1)
7STK Full-length insulin receptor bound with unsaturated insulin WT (2 insulins bound) asymmetric conformation (Conformation 2)
7MQO The insulin receptor ectodomain in complex with a venom hybrid insulin analogue - "head" region
7MQR The insulin receptor ectodomain in complex with four venom hybrid insulins - symmetric conformation
7MQS The insulin receptor ectodomain in complex with three venom hybrid insulin molecules - asymmetric conformation
7MD4 Insulin receptor ectodomain dimer complexed with two IRPA-3 partial agonists
7MD5 Insulin receptor ectodomain dimer complexed with two IRPA-9 partial agonists
7PG0 Low resolution Cryo-EM structure of full-length insulin receptor bound to 3 insulin with visible ddm micelle, conf 1
7PG2 Low resolution Cryo-EM structure of full-length insulin receptor bound to 3 insulin, conf 1
7PG3 Low resolution Cryo-EM structure of the full-length insulin receptor bound to 3 insulin, conf 2
7PG4 Low resolution Cryo-EM structure of the full-length insulin receptor bound to 2 insulin, conf 3
7QID tentative model of the human insulin receptor ectodomain bound by three insulin
7KD6 Insulin Receptor L1-CR plus alphaCT fragment in co-complex with Fv 83-7 and single-chain insulin SCI-b
7BW7 Cryo-EM Structure for the Ectodomain of the Full-length Human Insulin Receptor in Complex with 1 Insulin.
7BW8 Cryo-EM Structure for the Insulin Binding Region in the Ectodomain of the Full-length Human Insulin Receptor in Complex with 1 Insulin
7BWA Cryo-EM Structure for the Ectodomain of the Full-length Human Insulin Receptor in Complex with 2 Insulin
6VEP Human insulin in complex with the human insulin microreceptor in turn in complex with Fv 83-7
6VEQ Con-Ins G1 in complex with the human insulin microreceptor in turn in complex with Fv 83-7
6SOF human insulin receptor ectodomain bound by 4 insulin
6PXV Cryo-EM structure of full-length insulin receptor bound to 4 insulin. 3D refinement was focused on the extracellular region.
6PXW Cryo-EM structure of full-length insulin receptor bound to 4 insulin. 3D refinement was focused on the top part of the receptor complex.
6HN4 Leucine-zippered human insulin receptor ectodomain with single bound insulin - "lower" membrane-proximal part
6HN5 Leucine-zippered human insulin receptor ectodomain with single bound insulin - "upper" membrane-distal part
6CE7 Insulin Receptor ectodomain in complex with one insulin molecule
6CE9 Insulin Receptor ectodomain in complex with two insulin molecules
6CEB Insulin Receptor ectodomain in complex with two insulin molecules - C1 symmetry
5U1M Structure of the IRS-1 PTB Domain Bound to the Juxtamembrane Region of the Insulin Receptor
5KQV Insulin receptor ectodomain construct comprising domains L1,CR,L2, FnIII-1 and alphaCT peptide in complex with bovine insulin and FAB 83-14 (REVISED STRUCTURE)
5TQ1 Phospholipase C gamma-1 C-terminal SH2 domain bound to a phosphopeptide derived from the insulin receptor
5J3H Human insulin receptor domains L1-CR in complex with peptide S519C16 and 83-7 Fv
5HHW Crystal structure of insulin receptor kinase domain in complex with cis-(R)-7-(3-(azetidin-1-ylmethyl)cyclobutyl)-5-(3-((tetrahydro-2H-pyran-2-yl)methoxy)phenyl)-7H -pyrrolo[2,3-d]pyrimidin-4-amine.
4ZXB Structure of the human insulin receptor ectodomain, IRDeltabeta construct, in complex with four Fab molecules
5E1S The Crystal structure of INSR Tyrosine Kinase in complex with the Inhibitor BI 885578
4XSS Insulin-like growth factor I in complex with site 1 of a hybrid insulin receptor / Type 1 insulin-like growth factor receptor
4XST Structure of the endoglycosidase-H treated L1-CR domains of the human insulin receptor in complex with residues 697-719 of the human insulin receptor (A-isoform)
4XLV Crystal structure of the activated insulin receptor tyrosine kinase dimer
4OGA Insulin in complex with Site 1 of the human insulin receptor
2MFR Solution structure of the transmembrane domain of the insulin receptor in micelles
4IBM Crystal structure of insulin receptor kinase domain in complex with an inhibitor Irfin-1
3W11 Insulin receptor ectodomain construct comprising domains L1-CR in complex with human insulin, Alpha-CT peptide(704-719) and FAB 83-7
3W12 Insulin receptor ectodomain construct comprising domains L1-CR in complex with high-affinity insulin analogue [D-PRO-B26]-DTI-NH2, alpha-CT peptide(704-719) and FAB 83-7
3W13 Insulin receptor ectodomain construct comprising domains L1-CR in complex with high-affinity insulin analogue [D-PRO-B26]-DTI-NH2, alphact peptide(693-719) and FAB 83-7
3ETA Kinase domain of insulin receptor complexed with a pyrrolo pyridine inhibitor
3EKN Insulin receptor kinase complexed with an inhibitor
3EKK Insulin receptor kinase complexed with an inhibitor
2Z8C Phosphorylated insulin receptor tyrosine kinase in complex with (4-[5-carbamoyl-4-(3-methylanilino)pyrimidin-2-yl]aminophenyl)acetic acid
3BU3 Crystal structure of the insulin receptor kinase in complex with IRS2 KRLB peptide
3BU5 Crystal structure of the insulin receptor kinase in complex with IRS2 KRLB peptide and ATP
3BU6 Crystal structure of the insulin receptor kinase in complex with IRS2 KRLB phosphopeptide
2HR7 Insulin receptor (domains 1-3)
2B4S Crystal structure of a complex between PTP1B and the insulin receptor tyrosine kinase
2AUH Crystal structure of the Grb14 BPS region in complex with the insulin receptor tyrosine kinase
1RQQ Crystal Structure of the Insulin Receptor Kinase in Complex with the SH2 Domain of APS
1LK2 1.35A crystal structure of H-2Kb complexed with the GNYSFYAL peptide
1P14 Crystal structure of a catalytic-loop mutant of the insulin receptor tyrosine kinase
1I44 CRYSTALLOGRAPHIC STUDIES OF AN ACTIVATION LOOP MUTANT OF THE INSULIN RECEPTOR TYROSINE KINASE
1GAG CRYSTAL STRUCTURE OF THE INSULIN RECEPTOR KINASE IN COMPLEX WITH A BISUBSTRATE INHIBITOR
1IR3 PHOSPHORYLATED INSULIN RECEPTOR TYROSINE KINASE IN COMPLEX WITH PEPTIDE SUBSTRATE AND ATP ANALOG
1IRK CRYSTAL STRUCTURE OF THE TYROSINE KINASE DOMAIN OF THE HUMAN INSULIN RECEPTOR
Table 2. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary files icod.pdb and nati.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
Table 2. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary files icod.pdb and nati.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
PDB file name Residue A Atom A Residue B Atom B Distance (Å)
icod.pdb C_LYS_921 NZ F_GLU_1804 OE1 3.659
icod.pdb F_HIS_1799 NE2 F_GLU_1804 OE2 3.669
nati.pdb C_LYS_921 NZ F_GLU_1804 OE2 3.204
Table 3. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary file nati.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
Table 3. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary file nati.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
PDB file name Residue A Atom A Residue B Atom B Distance (Å)
nati.pdb C_LYS_921 NZ F_GLU_1804 OE2 3.204
Table 4. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary file icod.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
Table 4. Interfacial salt bridging network analysis [4] of the structural model of the insulin icodec bound to IR (supplementary file icod.pdb). In this table, the residue naming scheme is Chain ID_residue name_residue number.
PDB file name Residue A Atom A Residue B Atom B Distance (Å)
icod.pdb C_LYS_921 NZ F_GLU_1804 OE1 3.659
icod.pdb F_HIS_1799 NE2 F_GLU_1804 OE2 3.669
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