Cloning, sequencing and function ofsanA, a gene involved in nikkomycin biosynthesis ofStreptomyces ansochromogenes

Several genetically stable mutants blocked in nikkomycin biosynthesis were obtained after the slightly germinated spores ofStreptomyces ansochromogenes, 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 plasmid pIJ702 as cloning vector, NBB19 as cloning recipient. A 6 kb DNA fragment which can genetically complement NBB19 was cloned when screening the library for antifungal activity. Sequence analysis showed that the 3 kbBgl II -Sal I fragment contains one complete ORF (ORF1) and one partial ORF (ORF2). ORF1 is designated assanA. sanA is 1 365 bp, encoding a protein consisting of 454 amino acid residues. Database searching indicated thatsanA is homologous to the hypothetical methyltransferase inPyrococcus horikoshii with 25% identities and 41% positives. Disruptant ofsanA lost the ability to synthesize nikkomycin. It indicated thatsanA is a novel gene which is essential for nikkomycin biosynthesis.