Methods of identifying morphogen receptor-binding analogs

A method for identifying a binding analog of an OP-1 receptor, said analog being characterized as having substantially the same binding affinity for a cell surface receptor protein as OP-1, the method comprising:

• (a) providing a cell that expresses a surface receptor protein having binding specificity for OP-1 selected from:
• (i) a polypeptide comprising an amino acid sequence defined by residues 16-123 of SEQ ID NO:
• 4 (ALK-2);
• (ii) a polypeptide comprising an amino acid sequence defined by residues 24-152 of SEQ ID NO:
• 6 (ALK-3);
• (iii) a polypeptide comprising an amino acid sequence defined by residues 23-122 of SEQ ID NO:
• 8 (ALK-6);
• or
• (iv) a polypeptide having binding affinity for OP-1 and encoded by a first nucleic acid capable of hybridizing under stringent conditions with a second nucleic acid comprising the sequence defined by nucleotides 256-552 of SEQ ID NO:
• 7 (ALK-6), the stringent conditions being hybridization in 40% formamide 5×SSPE, 5×Denhardt's Solution, 0.1% SDS at 37° C. overnight, then washing in 0.1×SSPE, 0.1% SDS at 50° C.;
• (b) contacting said cell with a candidate OP-1 receptor-binding analog;
• and
• (c) detecting induction of an OP-1-mediated cellular response;
• wherein detection of induction of said OP-1-mediated cellular response is indicative that said candidate analog is an OP-1 receptor-binding analog.

A kit for identifying OP-1 or a candidate OP-1 receptor binding analog in a sample, the kit comprising:

• (a) a receptacle adapted to receive said sample, said receptacle containing a protein selected from:
• (i) a polypeptide comprising an amino acid sequence defined by residues 16-123 of SEQ ID NO:
• 4 (ALK-2);
• (ii) a polypeptide comprising an amino acid sequence defined by residues 24-152 of SEQ ID NO:
• 6 (ALK-3);
• (iii) a polypeptide comprising an amino acid sequence defined by residues 23-122 of SEQ ID NO:
• 8 (ALK-6);
• or
• (iv) a polypeptide having binding affinity for OP-1 and encoded by a first nucleic acid capable of hybridizing under stringent conditions with a second nucleic acid comprising the sequence defined by nucleotides 256-552 of SEQ ID NO:
• 7 (ALK-6), the stringent conditions being hybridization in 40% formamide 5×SSPE, 5×Denhardt's Solution, 0.1% SDS at 37° C. overnight, then washing in 0.1×SSPE, 0.1% SDS at 50° C.;
• and
• (b) means for detecting induction of an OP-1-mediated cellular response as a means for detecting interaction of OP-1 or a candidate OP-1 receptor-binding analog with said protein of part (a), said OP-1 or candidate analog comprising part of said sample provided to said receptacle.

A kit for identifying a binding analog for a morphogen receptor in a sample, said morphogen being characterized as sharing at least 60% amino acid sequence identity or at least 70% amino acid sequence homology with the sequence of the C-terminal 102 amino acids of SEQ ID NO:

• 7, and being able to substitute for OP-1 in binding to a protein comprising SEQ ID NOs. 4, 6, or 8, the kit comprising:
• (a) a receptacle adapted to receive said sample, said receptacle does not contain a Type II serine/threonine kinase morphogen receptor but contains protein selected from:
• (i) a polypeptide comprising an amino acid sequence defined by residues 16-123 of SEQ ID NO:
• 4 (ALK-2);
• (ii) a polypeptide comprising an amino acid sequence defined by residues 24-152 of SEQ ID NO:
• 6 (ALK-3);
• (iii) a polypeptide comprising an amino acid sequence defined by residues 23-122 of SEQ ID NO:
• 8 (ALK-6);
• or
• (iv) a polypeptide having binding affinity for OP-1 and encoded by a first nucleic acid capable of hybridizing under stringent conditions with a second nucleic acid comprising the sequence defined by nucleotides 256-552 of SEQ ID NO:
• 7 (ALK-6), the stringent conditions being hybridization in 40% formamide 5×SSPE, 5×Denhardt's Solution, 0.1% SDS at 37° C. overnight, then washing in 0.1×SSPE, 0.1% SDS at 50° C.;
• and
• (b) means for detecting specific binding interaction of OP-1 or said candidate analog with said protein of part (a), said OP-1 or candidate analog comprising part of said sample provided to said receptacle.