{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,2]],"date-time":"2025-08-02T19:24:14Z","timestamp":1754162654674,"version":"3.41.2"},"reference-count":33,"publisher":"Portland Press Ltd.","issue":"07","license":[{"start":{"date-parts":[[2025,6,23]],"date-time":"2025-06-23T00:00:00Z","timestamp":1750636800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2025,7,30]]},"abstract":"<jats:p>Enzymatic halogenation in natural products has been intensely investigated due to its potential utility as a tool to improve pharmacological and pharmaceutical properties of drug leads. Chlortetracycline (CTC), the first tetracycline (TC) antibiotic discovered nearly eight decades ago, contains a chlorine group. This chlorine is installed enzymatically by the flavin adenine dinucleotide (FAD)-dependent halogenase CtcP. CtcP and the FAD reductase CtcQ, which is also encoded in the CTC biosynthetic gene cluster, function as a two-component system. Structural information on CtcP and CtcQ has been lacking. In this study, we determined crystal structures of CtcP from Kitasatospora aureofaciens in a complex with polyethylene glycol and sulfate ions and in a complex with FAD, and a crystal structure of CtcQ in a complex with FAD and NAD. The structures of CtcP revealed a close similarity of this enzyme to the phenolic halogenase PltM, despite a large difference in the sizes of their respective substrates, presumably TC and phloroglucinol. The CtcP structure showed a conserved dimeric organization also found in PltM crystals. We showed that dimerization of CtcP is allosterically influenced by a distant C-terminal helical hairpin. A closed substrate-binding cavity of CtcP suggested that conformational changes were required to allow a substrate, likely not TC, to bind CtcP. We demonstrated that CtcP and CtcQ weakly bound each other. The dimeric structures of CtcP and CtcQ prompted us to propose approximate models of a 2:2\/CtcP:CtcQ complex, where FAD(H2) would shuttle between the two enzymes for chlorination and reduction.<\/jats:p>","DOI":"10.1042\/bsr20253185","type":"journal-article","created":{"date-parts":[[2025,6,23]],"date-time":"2025-06-23T07:02:33Z","timestamp":1750662153000},"page":"401-414","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Crystal structures and low-affinity complex formation of halogenase CtcP and FAD reductase CtcQ from the chlortetracycline biosynthetic pathway"],"prefix":"10.1042","volume":"45","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5335-8511","authenticated-orcid":false,"given":"Caixia","family":"Hou","sequence":"first","affiliation":[{"name":"1Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY 40536, U.S.A."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7961-5555","authenticated-orcid":false,"given":"Sylvie","family":"Garneau-Tsodikova","sequence":"additional","affiliation":[{"name":"1Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY 40536, U.S.A."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7094-4216","authenticated-orcid":false,"given":"Oleg V.","family":"Tsodikov","sequence":"additional","affiliation":[{"name":"1Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY 40536, U.S.A."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","published-online":{"date-parts":[[2025,7,4]]},"reference":[{"key":"2025073008471229600_BSR-2025-3185C1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/B978-0-12-398282-7.00001-1","article-title":"Occurrence of halogenated alkaloids","volume":"71","author":"Gribble","year":"2012","journal-title":"Alkaloids Chem. 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