{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T07:01:02Z","timestamp":1781247662129,"version":"3.54.1"},"reference-count":32,"publisher":"National Academy of Sciences","issue":"16","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1999,8,3]]},"abstract":"<jats:p>\n                    The assembly of the polyketide backbone of rifamycin B on the type I rifamycin polyketide synthase (PKS), encoded by the\n                    <jats:italic>rifA\u2013rifE<\/jats:italic>\n                    genes, is terminated by the product of the\n                    <jats:italic>rifF<\/jats:italic>\n                    gene, an amide synthase that releases the completed undecaketide as its macrocyclic lactam. Inactivation of\n                    <jats:italic>rifF<\/jats:italic>\n                    gives a rifamycin B nonproducing mutant that still accumulates a series of linear polyketides ranging from the tetra- to a decaketide, also detected in the wild type, demonstrating that the PKS operates in a processive manner. Disruptions of the\n                    <jats:italic>rifD<\/jats:italic>\n                    module 8 and\n                    <jats:italic>rifE<\/jats:italic>\n                    module 9 and module 10 genes also result in accumulation of such linear polyketides as a consequence of premature termination of polyketide assembly. Whereas the tetraketide carries an unmodified aromatic chromophore, the penta- through decaketides have undergone oxidative cyclization to the naphthoquinone, suggesting that this modification occurs during, not after, PKS assembly. The structure of one of the accumulated compounds together with\n                    <jats:sup>18<\/jats:sup>\n                    O experiments suggests that this oxidative cyclization produces an 8-hydroxy-7,8-dihydronaphthoquinone structure that, after the stage of proansamycin X, is dehydrogenated to an 8-hydroxynaphthoquinone.\n                  <\/jats:p>","DOI":"10.1073\/pnas.96.16.9051","type":"journal-article","created":{"date-parts":[[2002,7,26]],"date-time":"2002-07-26T10:35:07Z","timestamp":1027679707000},"page":"9051-9056","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":124,"title":["Direct evidence that the rifamycin polyketide synthase assembles polyketide chains processively"],"prefix":"10.1073","volume":"96","author":[{"given":"Tin-Wein","family":"Yu","sequence":"first","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; and School of Pharmacy and Department of Bacteriology, University of Wisconsin, Madison, WI 53706"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuemao","family":"Shen","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; and School of Pharmacy and Department of Bacteriology, University of Wisconsin, Madison, WI 53706"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yukiko","family":"Doi-Katayama","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; and School of Pharmacy and Department of Bacteriology, University of Wisconsin, Madison, WI 53706"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Li","family":"Tang","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; and School of Pharmacy and Department of Bacteriology, University of Wisconsin, Madison, WI 53706"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cheonseok","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; and School of Pharmacy and Department of Bacteriology, University of Wisconsin, Madison, WI 53706"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bradley S.","family":"Moore","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700; 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