Two new tailoring enzymes, a glycosyltransferase and an oxygenase, involved in biosynthesis of the angucycline antibiotic urdamycin A in Streptomyces fradiae Tü2717 This paper is dedicated to Professor Heinz Floss, a pioneer in the field of antibiotics, on the occasion of his 65th birthday. The GenBank accession numbers for the sequences reported in this paper are AF164960 and AF164961.

Abstract

Urdamycin A, the principal product of Streptomyces fradiae Tu $ 2717, is an angucycline-type antibiotic and anticancer agent containing C-glycosidically linked D-olivose. To extend knowledge of the biosynthesis of urdamycin A the authors have cloned further parts of the urdamycin biosynthetic gene cluster. Three new ORFs (urdK, urdJ and urdO) were identified on a 335 kb fragment, and seven new ORFs (urdL, urdM, urdJ2, urdZ1, urdGT2, urdG and urdH) on an 805 kb fragment. The deduced products of these genes show similarities to transporters (urdJ and urdJ2), regulatory genes (urdK), reductases (urdO), cyclases (urdL) and deoxysugar biosynthetic genes (urdG, urdH and urdZ1). The product of urdM shows striking sequence similarity to oxygenases (N-terminal sequence) as well as reductases (C-terminal sequence), and the deduced amino acid sequence of urdGT2 resembles those of glycosyltransferases. To determine the function of urdM and urdGT2, targeted gene inactivation experiments were performed. The resulting urdM deletion mutant strains accumulated predominantly rabelomycin, indicating that UrdM is involved in oxygenation at position 12b of urdamycin A. A mutant in which urdGT2 had been deleted produced urdamycin I, urdamycin J and urdamycin K instead of urdamycin A. Urdamycins I, J and K are tetracyclic angucyclinones lacking a C-C connected deoxysugar moiety. Therefore UrdGT2 must catalyse the earliest glycosyltransfer step in the urdamycin biosynthetic pathway, the C-glycosyltransfer of one NDP-D-olivose.

Identification of the Function of Gene lndM2 Encoding a Bifunctional Oxygenase-Reductase Involved in the Biosynthesis of the Antitumor Antibiotic Landomycin E by Streptomyces globisporus 1912 Supports the Originally Assigned Structure for Landomycinone

“…3 With the revised sequences in hand, we can put LanM2/LndM2 proteins in the group of UrdM-like bifunctional reductases-oxygenases, 15,20 which are common for angucycline biosynthesis. Indeed, in most cloned gene clusters for angucycline biosynthesis we encounter lanM2/lndM2 homologues.…”

“…Rabelomycin (9) was isolated from the mutant S. fradiae ΔM. 14,20 The feeding experiments were carried out using the mutant S. globisporus F133 10 in which the PKS-associated fourth ring cyclase gene lndF was inactivated. Thus, this mutant cannot produce any correctly cyclized polyketides 10 but can still express all downstream enzymes necessary for the landomycin E production when fed with an intermediate containing a completed polyketide moiety.…”

The TetR Family of Regulators

“…Thus, as is the case for ActR, at least one step in the induction of the LanK target operon involves the interaction of the repressor with an immature landomycin intermediate. TFRs are also located in the biosynthesis clusters for the related angucyclinone antibiotics urdamycin and saquayamycin, but the role of these TFRs in regulating antibiotic biosynthesis and export has not been investigated (83,84).…”

The C-Glycosylation of Flavonoids in Cereals

“…As a rare exception, a CGT that catalyzed the C-glucosylation of the siderophore enterobactin has been characterized in Escherichia coli (3). Similarly, an enzyme (UrdGT2) that C-conjugated a polyketide intermediate with D-olivose has also been identified as a component of the pathway leading to the biosynthesis of the antibiotic urdamycin A in Streptomyces fradiae (4,5). Analyses of the amino acid sequences of these two CGTs place them in family 1 of the 91 glycosyltransferase families classified to date (6).…”