Novel polyketide metabolites from Streptomyces rimosus mutant strain R1059.

Three novel polyketide metabolites were isolated from laboratory-scale fermentation of the Streptomyces rimosus mutant strain R1059. Structural elucidation of the compounds was based on NMR experiments. The compounds were characterized as naphthalene derivatives: (rel)-4beta,8-dihydroxy-3alpha-hydroxymethyl-4alpha-methyl-1,2,3,4-tetrahydronaphthalene1-one (1), 4xi8-dihydroxy-3-hydroxymethyl-4xi-methyl-1,4-dihydronaphthalene-1-one (2) and (rel)-4beta,8-dihydroxy-3alpha-O-[alpha-glucopyranosyl]hydroxymethyl-4alpha-methyl-1,2,3,4-tetrahydronaphthalene-1-one (3). The compounds isolated appear to be derived via a shorter polyketide backbone than oxytetracycline (4), the normal end-product made by the parent of this strain. Compound 3 was the glucoside of 1 and must be formed as a post-PKS reaction by the activation of a glycosyl transferase, which has not been reported in this species before.

Propionyl-CoA carboxylase from Streptomyces coelicolor A3(2): cloning of the gene encoding the biotin-containing subunit.

In Streptomyces coelicolor A3(2), polyketides are made from malonyl-CoA, which is presumed to be derived from acetyl-CoA by the action of acetyl-CoA carboxylase (ACC). No ACC activity was found in cell-free extracts of S. coelicolor. However, propionyl-CoA carboxylase (PCC) activity was detected at substantial levels. Fixation of CO2 by ACC and PCC occurs by covalent bonding of CO2 to a biotin-containing protein. Most bacteria have a single small biotinylated protein of approximately 22 kDa, but S. coelicolor contains three larger biotin-containing proteins (approximately 145, 88 and 70 kDa). To determine which biotinylated protein was associated with PCC activity, the enzyme was purified and shown to comprise an alpha subunit (biotin-containing) of 88 kDa and a beta subunit of 66 kDa. The N-terminal sequences of these proteins were determined and, using an oligonucleotide probe, the gene for the alpha subunit (pccA) was cloned.