The blasticidin S biosynthesis gene cluster from Streptomyces griseochromogenes:: Sequence analysis, organization, and initial characterization

Blasticidin S is a potent antifungal and cytotoxic peptidyl nucleoside antibiotic from Streptomyces griseochromogenes. The mixed biosynthesis of the compound is evident from the three distinct structural components a cytosine base, an amino deoxyglucoronic acid, and N-methyl beta-arginine. The blasticidin S biosynthesis gene cluster was cloned from S. griseochromogenes and the pathway heterologously expressed in S. lividans from a cosmid harboring a 36.7-kb fragment of S. griseochromogenes DNA. The complete DNA sequence of this insert has now been determined and evidence suggests a contiguous 20-kb section defines the blasticidin S biosynthesis cluster. The predicted functions of several open reading frames are consistent with the expect biochemistry and include and arginine 2,3-aminomutase a cytosylglucoronic acid synthase, and a guanidino N-methyltransferase insight into other steps in the assembly of blasticidin S was evident from sequence homology with proteins of known function and heterologous expression of fragments of the cluster. Additionally the gene that directs the production of free cytosine BisM, was subcloned and expressed in Escherichia coli. Characterization of BisM revealed that cytidine monophosphate serves as the precursor to cytosine.