Patent ID: 6927025

Claim:
A method of screening proteins and polypeptides to identfy a protein or polypeptide having a biological activity of interest, which comprises the sequential steps of (i) forming a first library, which comprises polynucleotide clones, (ii) expressing by in vitro transcription and translation an individual protein or polypeptide from each clone in the first library from a second library, which comprises individual proteins and polypeptides derived from each polynucleotide clone in the first library, (iii) assaying the second library to select an individual protein or polypeptide in the second library having a biological activity of interest; and (iv) identfying the protein or polypeptide selected in step (ii, by sequencing a polynucleotice clone from the first library that encodes the individual protein or polypeptide selected from the second library in step (iii), wherein the first library of polynucleotide clones in step (i) is a library of transformed bacterial cell colonies; the second library of individual proteins and polypeptides is formed by in vitro transcription and translation of a polynucleotide from each bacterial cell colony in step (ii); and the biological activity of interest in step (iii) is the ability to effect a post-translational modification of a protein or polypeptide from a tissue extract.