A second type-I PKS gene cluster isolated from Streptomyces hygroscopicus ATCC 29253, a rapamycin-producing strain.
Analysis of a 32.8-kb segment of DNA from the rapamycin (Rp) producer, Streptomyces hygroscopicus ATCC 29253, revealed a new type-I polyketide synthase (PKS) cluster consisting of four open reading frames (ORF 1-4), each encoding a single PKS module. The four ORFs are transcribed in the same direction and are flanked by several smaller ORFs (ORF 5-9), which may be related to the PKS cluster. The first PKS-containing ORF has a ligase domain at the N-terminus of the polypeptide. This domain has 55% aa identity to the CoA ligase domain of the Rp PKS (Schwecke et al., 1995. Proc. Natl. Acad. Sci. 92, 7839-7843) which is also encoded in this strain (Lowden et al., 1996. Angew. Chem. Int. Ed. Engl. 35, 2249-2251). ORF5 (340 aa) and ORF6 (924 aa) were found to be homologous to RapK (41% aa identity) and RapH (35% aa identity), which are hypothesized to be a pteridine-dependent dioxygenase and a regulatory protein, respectively (Molnar et al., 1996. Gene 169, 1-7). In addition, ORF7 (391 aa) was found to have up to 42% aa identity to a number of plant 3-deoxy-D-arabino-heptulosonate-7-phosphate synthases (DAHPS) and 47% aa identity to PhzF, a bacterial DAHPS involved in phenazine antibiotic synthesis. The proximity of the DAHPS-encoding gene to the PKS cluster containing a Rp-like ligase domain suggests that a derivative of shikimate may be used as the PKS starter. ORF8 (283 aa) was found to have homology (32% aa identity) to a Synechocystis sp. gene of unknown function. The N-terminal portion of ORF9 was found to be similar to a tetracycline 6-hydroxylase (34% aa identity) from Streptomyces aureofaciens.
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Antibacterial Discovery Research, Abbott Laboratories, Abbott Park, IL 60064, USA.
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D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000235:genetics; D000213:Acyl Carrier Protein / Q000235:genetics; D000217:Acyltransferases / Q000235:genetics; D000429:Alcohol Oxidoreductases / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D004269:DNA, Bacterial; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D006836:Hydro-Lyases / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics; D008025:Ligases; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D005810:Multigene Family; D016366:Open Reading Frames; D010088:Oxidoreductases / Q000235:genetics; D011090:Polyenes / Q000378:metabolism*; D020123:Sirolimus; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics
D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007527:Isoenzymes; D009097:Multienzyme Complexes; D011090:Polyenes; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C087192:polyketide synthase ketoreductase; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D000217:Acyltransferases; C078182:beta-ketoacyl-acyl carrier protein synthase I; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D006836:Hydro-Lyases; D008025:Ligases; D020123:Sirolimus