Random and combinatorial mutagenesis for improved total production of secretory target protein in Escherichia coli.

Signal peptides and secretory carrier proteins are commonly used to secrete heterologous recombinant protein in Gram-negative bacteria. The Escherichia coli osmotically-inducible protein Y (OsmY) is a carrier protein that secretes a target protein extracellularly, and we have previously applied it in the Bacterial Extracellular Protein Secretion System (BENNY) to accelerate directed evolution. In this study, we reported the first application of random and combinatorial mutagenesis on a carrier protein to enhance total secretory target protein production.