Patent ID: 8017559

Claim:
A method for the identification and isolation of a polypeptide capable of specifically binding to a target, said method comprising the steps of: (1) providing a nucleic acid library, wherein said library comprises a collection of nucleic acid molecules encoding an ensemble of polypeptides having the scaffold structure of a C-type lectin-like domain (CTLD) and a randomized CTLD loop region, said CTLD scaffold comprising the following structural elements: a) five β-strands and two α-helices sequentially appearing in the order β1, α1, α2, β2, β3, β4, and β5, the β-strands being arranged in two anti-parallel β-sheet composed of β1 and β5, the other β-sheet composed of β2, β3 and β4, and b) at least two disulfide bridges, one connecting α1 and β5 and one connecting β3 and a polypeptide segment connecting β4 and β5, and said randomized CTLD loop region consisting of two loop polypeptide segments, loop segment A (LSA) containing loops 1-4 and connecting β2 and β3, and loop segment B (LSB) containing loop 5 and connecting β3 and β4, wherein said CTLD loop region is randomized by substituting the portion of the nucleic acid molecules encoding some or all of the loop region with a nucleic acid fragment randomly selected from a multitude of nucleic acid fragments; (2) expressing the nucleic acid library in a display system to obtain an ensemble of polypeptides, in which the amino acid residues at least at one sequence position in the loop region differ between different members of said ensemble of polypeptides, wherein the amino acid residues differ at least at one sequence position in the loop region of amino acid residues 72-79 (loop 1), 81-85 (loop 2), 91-99 (loop 3), 101-107 (loop 4), and 114-117 (loop 5) of tetranectin SEQ ID NO: 276; (3) contacting the ensemble of polypeptides in step (2) with said target; and (4) isolating a polypeptide that is capable of specifically binding to said target from the ensemble of polypeptides in step (3).