Patent ID: 7598352

Claim:
A fibronectin type III (Fn3) polypeptide monobody derived from the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 3, the polypeptide monobody comprising: at least two adjacent Fn3 β-strand domain sequences selected from the group of A (residues 9-14 of SEQ ID NO: 2 and SEQ ID NO: 3), B (residues 17-21 of SEQ ID NO: 2 and SEQ ID NO: 3), C (residues 31-38 of SEQ ID NO: 2 and SEQ ID NO: 3), D (residues 46-50 of SEQ ID NO: 2 and SEQ ID NO: 3), E (residues 55-59 of SEQ ID NO: 2 and SEQ ID NO: 3), F (residues 67-75 of SEQ ID NO: 2 and SEQ ID NO: 3), and G (residues 88-94 of SEQ ID NO: 2 and SEQ ID NO: 3), with an associated loop region sequence linked between each pair of adjacent β-strand domain sequences, each of the loop region sequences being selected from the group of loops AB (residues 15-16 of SEQ ID NO: 2 and SEQ ID NO: 3), BC (residues 22-30 of SEQ ID NO: 2 and SEQ ID NO: 3), CD (residues 39-45 of SEQ ID NO: 2 and SEQ ID NO: 3), DE (residues 51-54 of SEQ ID NO: 2 and SEQ ID NO: 3), EF (residues 60-66 of SEQ ID NO: 2 and SEQ ID NO: 3), and FG residues 76-87 of SEQ ID NO: 2 and SEQ ID NO: 3); and optionally, an N-terminal tail of at least about 2 to about 33 amino acids, a C-terminal tail of at least about 2 to about 25 amino acids, or both; wherein at least one loop region sequence comprises a modified amino acid sequence which varies from a corresponding loop region present in SEQ ID NO:2 or SEQ ID NO:3 by deletion of up to all but one amino acid residue, insertion of two to about 25 amino acid residues, or replacement of two to all amino acid residues, and wherein the polypeptide monobody exhibits estrogen receptor binding activity via interaction of the at least one loop region sequence with the estrogen receptor.