Abstract: The present invention improves in vitro virus synthesis efficiency and stability of mRNA derived from screened cDNA in a cDNA display method to improve the efficiency and reliability of the production of a peptide by a molecular evolutionary engineering technique. Provided is a ligand which comprises three fingers formed from antiparallel ?-sheets and a loop region intercalated between the antiparallel ?-sheets, wherein at least a fingertip part formed by the loop region of each of the fingers is bound to the target molecule, and wherein the ligand comprises the amino acid sequence of SEQ ID NO: 1. In the amino acid sequence of SEQ ID NO: 1, X7 represents an arbitrary amino acid residue that constitutes the fingertip part of each of the fingers, each numeric character represents the number of amino acid residues, and X7 and X4 are not composed of the same amino acid residues as each other.

Abstract: The present invention improves in vitro virus synthesis efficiency and stability of mRNA derived from screened cDNA in a cDNA display method to improve the efficiency and reliability of the production of a peptide by a molecular evolutionary engineering technique. Provided is a ligand which comprises three fingers formed from antiparallel ?-sheets and a loop region intercalated between the antiparallel ?-sheets, wherein at least a fingertip part formed by the loop region of each of the fingers is bound to the target molecule, and wherein the ligand comprises the amino acid sequence of SEQ ID NO: 1. In the amino acid sequence of SEQ ID NO: 1, X7 represents an arbitrary amino acid residue that constitutes the fingertip part of each of the fingers, each numeric character represents the number of amino acid residues, and X7 and X4 are not composed of the same amino acid residues as each other.