CHARACTERIZATION AND TARGETED DISRUPTION OF A GLYCOSYLTRANSFERASE GENE IN THE TYLOSIN PRODUCER, STREPTOMYCES-FRADIAE

An open reading frame, designated tylN, has been identified by sequenc e analysis at one end of the tylosin biosynthetic gene cluster of Stre ptomyces fradiae, alongside a cluster of genes encoding the biosynthes is of NDP-deoxyallose. This 6-deoxyhexose sugar is converted to mycino se, via bis O-methylation, following attachment to the polyketide lact one during tylosin biosynthesis. The deduced product of tylN is simila r to several glycosyltransferases, authentic and putative, and display s a consensus sequence motif that appears to be characteristic of a su b-group of such enzymes. Specific disruption of tylN within the S. fra diae genome resulted in the production of demycinosyl-tylosin, whereas other glycosyltransferase activities involved in tylosin biosynthesis were not affected. Evidently, tylN encodes deoxyallosyl transferase. (C) 1998 Elsevier Science B.V. All rights reserved.