Construction and characterization of phage libraries displaying artificialproteins with random sequences

Three phage libraries, PL1, PL2, and PL3, displaying artificial proteins wi th random sequences were constructed. The artificial proteins, which are mo del of ancestral proteins, are derivatives of the 25 kinds of random protei ns with about 140 amino acid residues produced via random mutagenesis and c ombinatorial recombination. The random proteins were displayed on the surfa ce of filamentous bacteriophage as fusion protein with the pill coat protei n at an estimated average number on the phage particles in PL1, PL2, and PL 3 of 0.32, 0.32, and 0.08, respectively. Each library was shown to express 10(5) to 10(6) kinds of random proteins. With the phage libraries displayin g long random peptides, we now have an effective selection system to observ e in vitro evolution of new functional proteins from artificial proteins wi th random sequences.