Patent ID: 7612040

Claim:
A recombinant Lefty derivative polypeptide comprising an amino acid sequence as set forth in the formula: W-A-X-B-Y, wherein A consists essentially of an amino acid sequence at least 85% identical to the sequence of Region 2 of SEQ ID NO: 1; wherein B consists essentially of an amino acid sequence at least 85% identical to the sequence of Region 4 of SEQ ID NO: 1; wherein X consists of zero, one or more than one amino acid; wherein W consists of zero, one or more than one amino acid; wherein Y consists of zero, one or more than one amino acid; wherein the recombinant Lefty derivative polypeptide binds to one or more of Nodal, myostatin and GDF-11; wherein the recombinant Lefty derivative polypeptide is not a wild-type Lefty polypeptide; wherein the recombinant Lefty derivative polypeptide comprises an amino acid sequence that is at least 95% identical to a human Lefty polypeptide sequence selected from the group consisting of amino acids 78-353 of SEQ ID NO: 1 and amino acids 78-353 of SEQ ID NO:2; and wherein the recombinant Lefty derivative polypeptide comprises one or more mutations within the RXXR cleavage sequence corresponding to amino acid residues 132-135 of SEQ ID NO: 1 or 2 so as to prevent cleavage at the mutated sequence.