NUCLEOTIDE-SEQUENCE ANALYSIS OF THE CARBOMYCIN BIOSYNTHETIC GENES INCLUDING THE 3-O-ACYLTRANSFERASE GENE FROM STREPTOMYCES THERMOTOLERANS

A 3.2-kb DNA fragment of the carbomycin biosynthetic region including the 3-O-acyltransferase gene (acyA) from Streptomyces thermotolerans w as sequenced, and four ORFs were found in the fragment, The second ORF , designated ORF-A, was transcribed in the opposite direction to the o ther three ORFs, The first ORF was identified as carA, a gene for carb omycin resistance, The amino acid sequence of ORF-A was homologous to proteins of the cytochrome P-450 family, Streptomyces lividans transfo rmed with pCB20, in which ORF-A was subcloned, epoxidized carbomycin B at its C-12, 13 positions, thus producing carbomycin A, The third ORF , the amino acid sequence of which showed a homology to macrolide anti biotics O-acyltransferases was identified as acyA, The last ORF (ORF-B ), which starts just 3 bp downstream from the TGA termination codon of acyA, was thought to be a carbomycin 4-O-methyltransferase gene, beca use the amino acid sequence deduced from ORF-B showed high homology to a putative midecamycin 4-O-methyltransferase encoded on mdmC.