ORF6 from the clavulanic acid gene cluster of Streptomyces clavuligerus has ornithine acetyltransferase activity

Abstract

The clinically used beta-lactamase inhibitor clavulanic acid is produced by fermentation of Streptomyces clavuligerus. The orf6 gene of the clavulanic acid biosynthetic gene cluster in S. clavuligerus encodes a protein that shows sequence Homology to ornithine acetyltransferase (OAT), the fifth enzyme of the arginine biosynthetic pathway. Orf6 was overexpressed in Escherichia coli (at ≈15% of total soluble protein by SDS/PAGE analysis) indicating it was not toxic to the host cells. The recombinant protein was purified (to >95% purity)byaone-step technique. Like other OATs it was synthesized as a precursor protein which underwent autocatalytic internal cleavage in E. coli to generate α and β ..