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Unformatted text preview: An I terative Nonribosomal Peptide Synthetase Assembles the Pyrrole-Amide Antibiotic Congocidine in Streptomyces ambofaciens S. ambofaciens chromosome gene cluster directs congocidine biosynthesis 9 genes are involved in regulation, resistance, or congocidine assembly. Congocidine is assembled by nonribosomal peptide synthetase (NRPS) which is encoded by 4 gnes. NRPS contain module and several single domain proteins. I ntro Streptomyces produce pyrrole-amides (oligopyrroles or oligopeptidess) that has antiviral, antibiotic, antitumor activities. Members of pyrrole-amide family are congocidine (also called netropsin) and distamycin. Both have ability to bind to the minor groove of DNA double helix. They bind DNA reversibly through H bonds, van der Waals contacts, and electrostatic interactions ( but not covalently) at sequences of 4 or more consecutive A-T pairs and strongly discriminate against G-C pairs. Therefore they are used as sequene selective. recent discovery shows pyrronamycin B binds DNA covalently. Biosynthesis of congocidine: originate from arginine. The linear chromosome of this bacterium have been sequenced. Gene cluster found in the arms of streptomyces chromosome. Identification, delimitation, and analysis of gene cluster were done to find out whether the biosynthesis of congocidine is directed by the gene cluster. Studies show the congocidine is assembled by NRPS. NRPS contains a unique adenylation domain that acts iteractively and a condensation domain that uses CoA-activated rather than PCP activated guanidinoacetate as substrate....
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- Spring '07