{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,5,10]],"date-time":"2025-05-10T09:07:50Z","timestamp":1746868070707,"version":"3.37.3"},"reference-count":42,"publisher":"Portland Press Ltd.","issue":"14","license":[{"start":{"date-parts":[[2022,6,30]],"date-time":"2022-06-30T00:00:00Z","timestamp":1656547200000},"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":[[2022,7,29]]},"abstract":"<jats:p>KaiC, a core protein of the cyanobacterial circadian clock, consists of an N-terminal CI domain and a C-terminal CII domain, and assembles into a double-ring hexamer upon binding with ATP. KaiC rhythmically phosphorylates and dephosphorylates its own two adjacent residues Ser431 and Thr432 at the CII domain with a period of \u223c24\u2005h through assembly and disassembly with the other clock proteins, KaiA and\/or KaiB. In this study, to understand how KaiC alters its conformation as the source of circadian rhythm, we investigated structural changes of an inner-radius side of the CII ring using time-resolved Trp fluorescence spectroscopy. A KaiC mutant harboring a Trp fluorescence probe at a position of 419 exhibited a robust circadian rhythm with little temperature sensitivity in the presence of KaiA and KaiB. Our fluorescence observations show a remarkable environmental change at the inner-radius side of the CII ring during circadian oscillation. Crystallographic analysis revealed that a side chain of Trp at the position of 419 was oriented toward a region undergoing a helix\u2013coil transition, which is considered to be a key event to allosterically regulate the CI ring that plays a crucial role in determining the cycle period. The present study provides a dynamical insight into how KaiC generates circadian oscillation.<\/jats:p>","DOI":"10.1042\/bcj20210544","type":"journal-article","created":{"date-parts":[[2022,6,30]],"date-time":"2022-06-30T13:27:06Z","timestamp":1656595626000},"page":"1505-1515","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Highly sensitive tryptophan fluorescence probe for detecting rhythmic conformational changes of KaiC in the cyanobacterial circadian clock system"],"prefix":"10.1042","volume":"479","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6736-631X","authenticated-orcid":false,"given":"Atsushi","family":"Mukaiyama","sequence":"first","affiliation":[{"name":"1Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"},{"name":"2Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yoshihiko","family":"Furuike","sequence":"additional","affiliation":[{"name":"1Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"},{"name":"2Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eiki","family":"Yamashita","sequence":"additional","affiliation":[{"name":"3Institute for Protein Research, Osaka University, 3-2 Yamada-oka, Suita 565-0871, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shuji","family":"Akiyama","sequence":"additional","affiliation":[{"name":"1Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"},{"name":"2Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","published-online":{"date-parts":[[2022,7,19]]},"reference":[{"key":"2022071916272953800_BCJ-2021-0544CC1","doi-asserted-by":"publisher","first-page":"2112","DOI":"10.1073\/pnas.68.9.2112","article-title":"Clock mutants of Drosophila melanogaster","volume":"68","year":"1971","journal-title":"Proc. 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