Improvement of an unusual twin-arginine transporter leader peptide by a codon-based randomization approach.

Secretion of Escherichia coli penicillin acylase was improved by codon-based random mutagenesis of its signal peptide. The mutagenesis technology was applied to the gene region coding for positions Lys2 to Thr13 (N half) and Ala14 to Leu25 (C half) of the signal peptide. Protein secretion was higher in several signal peptide variants (up to fourfold with respect to the wild-type value).