ANALYSIS OF 7 GENES FROM THE ERYAL -ERYK REGION OF THE ERYTHROMYCIN BIOSYNTHETIC GENE-CLUSTER IN SACCHAROPOLYSPORA-ERYTHRAEA/

The gene cluster (ery) governing the biosynthesis of the macrolide ant ibiotic erythromycin A by Saccharopolyspora erythraea contains, in add ition to the eryA genes encoding the polyketide synthase, two regions containing genes for later steps in the pathway. The region 5' of eryA , and lying between eryA and the gene eryK, which is known to encode t he C-12 hydroxylase, has been sequenced and shown to contain seven add itional open reading frames (ORFs 13-19). On the basis of sequence sim ilarities, roles are proposed for several of these ORFs in the biosynt hesis of the deoxysugar mycarose and the deoxyaminosugar desosamine. A chromosomal mutant carrying a deletion in ORF15 has been constructed and shown to accumulate 3-O-mycarosyl-erythronolide B, as expected for an eryC mutant. Similarly, a chromosomal mutant carrying a deletion i n ORF16 has been constructed and shown to accumulate erythronolide B, as expected for an eryB mutant.