Modified Fusion Polypeptides

Abstract

Chimeric polypeptides wherein the polypeptides comprise a modified binding domain of growth hormone linked to a receptor binding domain of growth hormone receptor; and tandems/oligomers of such modified growth hormone binding domains.

1 . A fusion polypeptide comprising: 
       i) a first modified growth hormone receptor binding domain of growth hormone wherein said modification is the addition, deletion or substitution of at least one amino acid residue; and 
       ii) a second modified growth hormone receptor binding domain of growth hormone wherein said modification is the addition deletion or substitution of at least one amino acid residue, 
       wherein
 said binding domains are fused in tandem; 
 the modification is to site 2 in at least one binding domain of growth hormone, and 
 said polypeptide is an antagonist of growth hormone receptor. 
 
     
     
         2 . A polypeptide according to  claim 1 , wherein said first and second binding domains are also modified in site 1 of growth hormone. 
     
     
         3 . A polypeptide according to  claim 1 , wherein said first and second binding domains are modified in site 2 of growth hormone. 
     
     
         4 . A polypeptide according to  claim 1 , wherein said modification is to binding domains of both site 1 and site 2 of growth hormone. 
     
     
         5 . A polypeptide according to  claim 2 , wherein said modification comprises at least one amino acid substitution in the growth hormone amino acid sequence of SEQ ID NO:5 selected from the group consisting of: histidine 18 with alanine or aspartic acid; histidine 21 with asparagine; glutamine 22 with alanine; phenylalanine 25 with alanine; aspartic acid 26 with alanine; glutamine 29 with alanine; glutamic acid 167 with alanine; aspartic acid 171 with serine; lysine 172 with serine or alanine; and isoleucine 179 with tyrosine. 
     
     
         6 . A polypeptide according to  claim 5 , wherein said modification consists of the following amino acid substitutions in the growth hormone amino acid sequence of SEQ ID NO:5: histidine 18 aspartic acid; histidine 21 asparagine; arginine 167 asparagine; aspartic acid 171 arginine; glutamic acid 174 serine; and isoleucine 179 threonine. 
     
     
         7 . A polypeptide according to  claim 5 , wherein said modification consists of the following amino acid substitutions in the growth hormone amino acid sequence of SEQ ID NO:5: histidine 18 alanine; glutamine 22 alanine; phenylalanine 25 alanine; aspartic acid 26 alanine; glutamine 29 alanine; glutamic acid 65 alanine; lysine 168 alanine; and glutamic acid 174 alanine. 
     
     
         8 . A polypeptide according to  claim 1 , wherein said site 2 modification is to amino acid residue glycine 120 of the amino acid sequence of SEQ ID NO: 5. 
     
     
         9 . A polypeptide according to  claim 8 , wherein said site 2 modification is a substitution of glycine for an amino acid selected from the group consisting of arginine, alanine, lysine, tryptophan, tyrosine, phenylalanine, and glutamic acid. 
     
     
         10 . A polypeptide according to  claim 9 , wherein said site 2 substitution is glycine 120 for arginine or lysine or alanine. 
     
     
         11 . A polypeptide according to  claim 1 , wherein the first modified binding domain of growth hormone is linked by a linker to the second growth hormone binding domain. 
     
     
         12 . A polypeptide according to  claim 11 , wherein the linker is a polypeptide which comprises 5 to 30 amino acid residues. 
     
     
         13 . A polypeptide according to  claim 12 , wherein the linker comprises 10 to 20 amino acid residues. 
     
     
         14 . A polypeptide according to  claim 12 , wherein the linker comprises at least one copy of the peptide Gly Gly Gly Gly Ser (SEQ ID NO:7). 
     
     
         15 . A nucleic acid molecule which encodes a polypeptide according to  claim 1 . 
     
     
         16 . A vector comprising a nucleic acid molecule according to  claim 15 . 
     
     
         17 . A pharmaceutical composition comprising a polypeptide according to  claim 1 , and a pharmaceutically-acceptable carrier. 
     
     
         18 . An isolated cell transformed with the nucleic acid or vector according to  claim 15 . 
     
     
         19 . A method of treating growth hormone excess in a human subject, said method comprising administering to said human subject an effective amount of a polypeptide according to  claim 1 .