Homology between Streptomyces genes coding for synthesis of different polyketides used to clone antibiotic biosynthetic genes

Abstract

Many important antibiotics such as tetracyclines, erythromycin, adriamycin, monensin, rifamycin and avermectins are polyketides. In their biosynthesis, multifunctional synthases catalyse iterated condensation of thio-esters derived from acetate, propionate or butyrate to yield aliphatic chains of varying length and carrying different alkyl substituents. Subsequent modifications, including aromatic or macrolide ring closure or specific methylations or glycosylations, generate further chemical diversity. It has been suggested that, if different polyketide synthases had a common evolutionary origin, cloned DNA coding for one synthase might be used as a hybridization probe for the isolation of others. We show here that this is indeed possible. Study of a range of such synthase genes and their products should help to elucidate what determines the choice and order of condensation of different residues in polyketide assembly, and might yield, by in vitro recombination or mutagenesis, synthase genes capable of producing novel antibiotics. Moreover, because genes for entire antibiotic pathways are usually clustered in Streptomyces, cloned polyketide synthase genes are valuable in giving access to groups of linked biosynthetic genes.

Cloning and characterization of polyketide synthase genes for jadomycin B biosynthesis in Streptomyces venezuelae ISP5230

“…(1 987a,b), three of seven streptomycetes not then known to produce polyketidederived metabolites, unexpectedly gave genomic DNA fragments that hybridized with the act probes. One of these, Streptomyesparvzlh was later found to produce the polyketide-derived antibiotic nonactin (cited by Malpartida et al , 1987b), and Streptomyes venepzlehe ISP5230 was subsequently reported to produce jadomycins (Ayer e t al., 1991), a group of pigmented compounds believed from the pattern of isotopic labelling with [13C]acetate to be of polyketide origin (S. Ayer, personal communication). Jadomycin B, the main component of the mixture produced during growth in an isoleucine-containing medium, is glycosylated and has an isoleucine moiety fused into the cyclic structure (Fig.…”

Cloning and heterologous expression of the entire gene clusters for PD 116740 from Streptomyces strain WP 4669 and tetrangulol and tetrangomycin from Streptomyces rimosus NRRL 3016

“…Molecular genetic analyses have revealed that the genes for each PKS are clustered in a relatively small region of DNA (22). The gene clusters for numerous polyketide pathways have been detected by hybridization with probes derived from genes coding for proteins that catalyze equivalent reactions in different pathways (25,29).Angucyclinones, a name recently given to naturally occurring benz [a]anthraquinones, are a rapidly growing group of polyketide natural products, involving many bioactive compounds (41). They are now the largest class of known aromatic decaketides.…”

An acyl-coenzyme A carboxylase encoding gene associated with jadomycin biosynthesis in Streptomyces venezuelae ISP5230 The GenBank accession number for the sequence reported in this paper is AF126429.

“…The jad gene cluster was detected by hybridization with the act PKS genes of Streptomyces coelicolor A3(2) (Malpartida et al, 1987 ;Han et al, 1994), and fragments were identified from a restriction map of the region subcloned for sequencing in the phagemid pBluescript II.  analysis (Devereux et al, 1984) of the 2n4 kb EcoRIBamHI segment located two ORFs, assigned to jadI and jadJ.…”