Cloning, sequencing and function of sanA, a gene involved in nikkomycin biosynthesis of Streptomyces ansochromogenes

Several genetically stable mutants blocked in nikkomycin biosynthesis were obtained after the slightly germinated spores of Streptomyces ansochromogen es, a nikkomycin producer, were treated with ultra violet radiation. One of the mutants is the same in morpholotical differentiation as the wild type strain and is designated as NBB19. A DNA library was constructed using plas mid pIJ702 as cloning vector, NBB19 as cloning recipient. A 6 kb DNA fragme nt which can genetically complement NBB19 was cloned when screening the lib rary for antifungal activity. Sequence analysis showed that the 3 kb Bgl II -Sal I fragment contains one complete ORF (ORF1) and one partial ORF (ORF2) . ORF1 is designated as sanA. sanA is 1 365 bp, encoding a protein consisti ng of 454 amino acid residues. Database searching indicated that sanA is ho mologous to the hypothetical methyltransferase in Pyrococcus horikoshii wit h 25% identities and 41% positives. Disruptant of sanA lost the ability to synthesize nikkomycin. It indicated that sanA is a novel gene which is esse ntial for nikkomycin biosynthesis.