Identification of a set of genes involved in the biosynthesis of the aminonucleoside moiety of antibiotic A201A from Streptomyces capreolus

Abstract

A novel cosmid (pABC6.5) whose DNA insert from Streptomyces capreolus, the A201A antibiotic producer, overlaps the inserts of the previously reported pCAR11 and pCAR13 cosmids, has been isolated. These two latter cosmids were known to contain the aminonucleoside antibiotic A201A resistance determinants ard2 and ard1, respectively. Together, these three cosmids have permitted the identification of a DNA stretch of 19 kb between ard1 and ard2, which should comprise a large region of a putative A201A biosynthetic (ata) gene cluster. The sequence of the 7 kb upstream of ard1 towards ard2 reveals seven consecutive open reading frames: ataP3, ataP5, ataP4, ataP10, ataP7, ata12 and ataPKS1. Except for the last two, their deduced products present high similarities to an identical number of counterparts from the pur cluster of Streptomyces alboniger that were either known or proposed to be implicated in the biosynthesis of the N6,N6-dimethyl-3′-amino-3′-deoxyadenosine moiety of puromycin. Because A201A contains this chemical moiety, these ataP genes are most likely implicated in its biosynthesis. Accordingly, the ataP4, ataP5 and ataP10 genes complemented specific puromycin nonproducing Δpur4, Δpur5 and Δpur10 mutants of S. alboniger, respectively. Amino acid sequence comparisons suggest that ata12 and ataPKS1 could be implicated in the biosynthesis of the D-rhamnose and α-p-coumaric acid moieties of A201A. Further sequencing of 2 kb of DNA downstream of ard1 has disclosed a region which might contain one end of the ata cluster.