engleski

Ablation of the otcC gene encoding a post-polyketide hydroxylase from the oxytetracyline biosynthetic pathway in Streptomyces rimosus results in novel polyketides with altered chain length

Oxytetracycline (OTC) is a 19 carbon polyketide antibiotic made by Streptomyces rimosus. The otcC gene encodes an anhydrotetracycline oxygenase that catalyses a hydroxylation of the anthracycline structure at position C6 after biosynthesis of the polyketide backbone is completed. A recombinant strain of S. rimosus that was disrupted in the genomic copy of otcC synthesized a novel C-17 polyketide. This result indicates that the absence of the otcC gene product significantly influences the ability of the OTC ‘ minimal’ polyketide synthase (PKS) to make a polyketide product of the correct chain length. A mutant copy of otcC was made by site-directed mutagenesis of three essential glycine codons located within the putative NADPH-binding domain. The mutant gene was expressed in E. coli and biochemical analysis confirmed that the gene product was catalytically-inactive. When the mutant gene replaced the ablated gene in the chromosome of S. rimosus, the ability to make a 19-carbon backbone was restored, indicating that OtcC is an essential partner in the quaternary structure of the synthase complex.

Streptomyces rimosus; oxytetracycline; otcC gene; anhydrotetracycline oxygenase; polyketide synthase; novel polyketides

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