Structure and Function of sanV: a gene involved in nikkomycin biosynthesis of Streptomyces ansochromogenes.

A 6.3-kb BamHI-BglII DNA fragment was cloned from cos20 by using chromosome walking strategy. It was partially sequenced with the result that there is a possible ORF of 1272 nucleotides. The ORF designated sanV was deposited in GenBank under accession no. AF469955. Database search indicated that the deduced protein of sanV shows 28% identity and 44% similarity over 405 amino acid residues to the large component (E) of glutamate mutases from Clostridium cochlearium. Gene disruption was performed to study the function of sanV. It was found that sanV disruptants exhibited much poorer inhibition to the test strain than the wild-type S. ansochromogenes 7100. Furthermore, HPLC analysis indicated that the sanV disruptants almost did not produce nikkomycins X and Z, whereas they accumulated new nikkomycins Ox and Oz, which revealed that sanV is an important gene involved in the biosynthesis of the peptidyl moiety of nikkomycins. Streptomyces ansochromogenes , isolated from the soil in northeastern China, produces nikkomycins that belong to the group of peptidyl nucleoside antibiotics. They are