{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T07:03:47Z","timestamp":1790147027277,"version":"4.0.1"},"reference-count":41,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"},{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP25ama1210015564"],"award-info":[{"award-number":["JP25ama1210015564"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100009619","name":"Japan Agency for Medical Research and Development","doi-asserted-by":"publisher","award":["JP25ama1210014142"],"award-info":[{"award-number":["JP25ama1210014142"]}],"id":[{"id":"10.13039\/100009619","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Proteins"],"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>\n                    The cyanobacterial circadian clock is driven by a core post\u2010translational oscillator composed of KaiA, KaiB, and KaiC, with the histidine kinase (HK), SasA, acting as the primary transducer of timing signals for downstream gene expression. Despite its central role, the structural architecture, oligomeric assembly of full\u2010length SasA, and its stoichiometric interactions with the KaiC hexamer remain unclear. Herein, we determined the crystal structure of the SasA C\u2010terminal ATPase domain (SasA\n                    <jats:sub>C<\/jats:sub>\n                    ) from\n                    <jats:italic>Thermosynechococcus vestitus<\/jats:italic>\n                    BP\u20101 at 2.31\u2009\u00c5 resolution. SasA\n                    <jats:sub>C<\/jats:sub>\n                    adopts a canonical GHKL family fold but features a distinct G2\u2010box (ATP lid) orientation that differs markedly from other prototypical HKs. Mass photometry (MP) analysis of wild\u2010type SasA and a truncated sensory domain mutant revealed that SasA undergoes concentration\u2010dependent, even\u2010numbered oligomerization (monomer\u2013dimer\u2013tetramer), establishing that SasA is predominantly a dimeric HK rather than the previously proposed trimeric or hexameric forms. Interaction assays demonstrated that the KaiC hexamer formed discrete complexes containing two or four SasA molecules, corresponding to 2:6 and 4:6 (SasA:KaiC) stoichiometries. These results provide a structural and biophysical framework for understanding SasA assembly with KaiC in the cyanobacterial circadian output pathway.\n                  <\/jats:p>","DOI":"10.1002\/prot.70184","type":"journal-article","created":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T06:37:56Z","timestamp":1790145476000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Structural and Biophysical Basis of Circadian Output Kinase\n                    <scp>SasA<\/scp>\n                    and Its Discrete Stoichiometric Assembly With the\n                    <scp>KaiC<\/scp>\n                    Hexamer"],"prefix":"10.1002","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2033-486X","authenticated-orcid":false,"given":"Sota W.","family":"Suzuki","sequence":"first","affiliation":[{"name":"Graduate School of Science Toho University  Funabashi Chiba Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5302-9005","authenticated-orcid":false,"given":"Yuki","family":"Hirato","sequence":"additional","affiliation":[{"name":"Faculty of Science Toho University  Funabashi Chiba Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takahiro","family":"Iida","sequence":"additional","affiliation":[{"name":"Faculty of Science Toho University  Funabashi Chiba Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1429-1844","authenticated-orcid":false,"given":"Takahisa","family":"Ikegami","sequence":"additional","affiliation":[{"name":"Graduate School of Medical Life Science Yokohama City University  Yokohama Kanagawa Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9317-0521","authenticated-orcid":false,"given":"Masaru","family":"Goto","sequence":"additional","affiliation":[{"name":"Faculty of Science Toho University  Funabashi Chiba Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0069-8931","authenticated-orcid":false,"given":"Risa","family":"Mutoh","sequence":"additional","affiliation":[{"name":"Faculty of Science Toho University  Funabashi Chiba Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"key":"e_1_2_10_2_1","first-page":"118","volume-title":"The Physiological Clock","author":"B\u00fcnning 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