STRUCTURE OF THE C-TERMINAL REGION OF THE INSULIN RECEPTOR a-CHAIN AND OF THE INSULIN-LIKE GROWTH FACTOR RECEPTOR a-CHAIN

Abstract

The present invention relates generally to structural studies of the insulin binding site of the insulin receptor (IR) and the insulin-like growth factor 1 receptor (IGF-1R). More particularly, the present invention relates to the crystal structure of the low affinity insulin binding site of the IR ectodomain comprising the C-terminal region of the IR α-chain, as well as the corresponding region of IGF-1R, and to methods of using the crystal and related structural information to screen for and design compounds that interact with or modulate the function of IR and/or IGF-1R.

1 . A computer-assisted method of identifying, designing or screening for a compound that can potentially interacts with insulin-like growth factor-1 receptor (IGF-1R), which method comprises
 (a) fitting the structure of a candidate compound to the structure of the low affinity insulin binding site of the IGF-1R, the structure having atomic coordinates shown in of one or more of Appendixes II IV, and VI, or a subset of atomic coordinates at least representing the C-terminal region of the α-chain of IGF-1R; and
 (b) detecting compounds having an energetically favoured interaction with a structure defined by the atomic coordinates of amino acids 681-697 of the IGF-1R α-chain (SEQ ID NO: 15), or a mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R, wherein the mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R is S519C16 (SEQ ID NO: 18). 
   
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1 , further comprising synthesising or obtaining an identified or designed candidate compound and determining the ability of the candidate compound to interact with IGF-1R. 
     
     
         4 . The method according to  claim 1 , wherein the atomic coordinates of step (a) define one or more regions of the low affinity binding site of IGF-1R for IGF comprising the C-terminal region of the α-chain of IGF-1R, or a mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R, wherein the mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R is S519C16 (SEQ ID NO: 18). 
     
     
         5 - 12 . (canceled) 
     
     
         13 . The method according to  claim 1 , wherein the atomic coordinates of step (a) defining the low affinity IGF binding site of IGF-1R further comprise the L1 domain and/or the CR domain of IGF-1R ectodomain. 
     
     
         14 . The method according to  claim 13 , wherein the atomic coordinates of step (a) define the central β-sheet of the L1 domain, and/or that part of the second LRR containing Ser35, and/or the loop in the fourth LRR rung of the L1 domain. 
     
     
         15 . The method according to  claim 13 , wherein the atomic coordinates of step (a) define module 6 of the CR domain of IGF-1R. 
     
     
         16 - 17 . (canceled) 
     
     
         18 . The method according to  claim 3 , wherein the candidate compound for interacting with IGF-1R is chemically modified as a result of structure-based evaluation. 
     
     
         19 . The method according to  claim 18 , wherein the chemical modification is designed to either:
 (i) reduce the potential for the candidate compound to bind to IR whilst maintaining binding to IGF-1R; or   (ii) reduce the potential for the candidate compound to bind to IGF-1R, whilst maintaining binding to IR.   
     
     
         20 - 26 . (canceled) 
     
     
         27 . A computer-assisted method of identifying a compound that potentially interacts with IR and/or IGF-1R, which method comprises fitting the structure of:
 (i) the low affinity insulin binding site of IR, the structure being defined by the atomic coordinates shown in one or more of Appendixes I, III and V;   (ii) the low affinity IGF binding site of IGF-1R, the structure being defined by the atomic coordinates shown in one or more of Appendixes II, IV and VI; and/or   (iii) the C-terminal region of the α-chain of IR, the C-terminal region of the α-chain of IGF-1R, or a mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R, the structure being defined by a subset of atomic coordinates shown in one or more of Appendixes I to VI, to the structure of a candidate compound.   
     
     
         28 - 29 . (canceled) 
     
     
         30 . A method for evaluating the ability of a compound to interact with IR and/or IGF-1R, the method comprising the steps of:
 (a) employing computational means to perform a fitting operation between the compound and the binding surface of a computer model of the low affinity binding site for insulin on IR ectodomain, and/or the low affinity binding site for IGF on IGF-1R ectodomain, using atomic coordinates wherein the root mean square deviation between the atomic coordinates and atomic coordinates of one or more of Appendixes I to VI or a subset of atomic coordinates of one or more thereof at least representing the C-terminal region of the α-chain of IR, the C-terminal region of the α-chain of IGF-1R, or a mimetic of the C-terminal region of the α-chain of IR and/or IGF-1R, is not more than 1.5 Å; and   (b) analysing the results of the fitting operation to quantify the association between the compound and the binding surface model.   
     
     
         31 - 40 . (canceled)