title: Structural basis of the day-night transition in a bacterial circadian clock.
abstract: Circadian clocks are ubiquitous timing systems that induce rhythms of biological activities in synchrony with night and day. In cyanobacteria, timing is generated by a posttranslational clock consisting of KaiA, KaiB, and KaiC proteins and a set of output signaling proteins, SasA and CikA, which transduce this rhythm to control gene expression. Here, we describe crystal and nuclear magnetic resonance structures of KaiB-KaiC,KaiA-KaiB-KaiC, and CikA-KaiB complexes. They reveal how the metamorphic properties of KaiB, a protein that adopts two distinct folds, and the post-adenosine triphosphate hydrolysis state of KaiC create a hub around which nighttime signaling events revolve, including inactivation of KaiA and reciprocal regulation of the mutually antagonistic signaling proteins, SasA and CikA.
authors.affiliation: Quantitative and Systems Biology, University of California, Merced, CA 95343, USA.
authors.forename: Roger
authors.identifier: 0000-0002-2188-0321
authors.initials: R
authors.lastname: Tseng
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Nicolette F
authors.identifier: 0000-0001-6557-9349
authors.initials: NF
authors.lastname: Goularte
authors.affiliation: School of Natural Sciences, University of California, Merced, CA 95343, USA.
authors.forename: Archana
authors.identifier: 0000-0002-5691-8094
authors.initials: A
authors.lastname: Chavan
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Jansen
authors.identifier: 0000-0002-4323-657X
authors.initials: J
authors.lastname: Luu
authors.affiliation: Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Susan E
authors.identifier: 0000-0003-3487-1990
authors.initials: SE
authors.lastname: Cohen
authors.affiliation: School of Natural Sciences, University of California, Merced, CA 95343, USA.
authors.forename: Yong-Gang
authors.identifier: 0000-0002-5096-564X
authors.initials: YG
authors.lastname: Chang
authors.affiliation: Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA.
authors.forename: Joel
authors.identifier: 0000-0002-2703-3035
authors.initials: J
authors.lastname: Heisler
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Alicia K
authors.initials: AK
authors.lastname: Michael
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Sarvind
authors.identifier: 0000-0002-6959-0577
authors.initials: S
authors.lastname: Tripathi
authors.affiliation: Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.|Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Susan S
authors.identifier: 0000-0002-4264-7019
authors.initials: SS
authors.lastname: Golden
authors.affiliation: Quantitative and Systems Biology, University of California, Merced, CA 95343, USA. aliwang@ucmerced.edu cpartch@ucsc.edu.|School of Natural Sciences, University of California, Merced, CA 95343, USA.|Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.|Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA.|Health Sciences Research Institute, University of California, Merced, CA 95343, USA.
authors.forename: Andy
authors.identifier: 0000-0003-4741-6946
authors.initials: A
authors.lastname: LiWang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA. aliwang@ucmerced.edu cpartch@ucsc.edu.|Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Carrie L
authors.identifier: 0000-0002-4677-2861
authors.initials: CL
authors.lastname: Partch
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D057906:Circadian Clocks; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000737:chemistry* / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000201:enzymology / Q000502:physiology*; D006868:Hydrolysis; D019906:Nuclear Magnetic Resonance, Biomolecular; D000072417:Protein Domains; D011494:Protein Kinases / Q000737:chemistry* / Q000648:ultrastructure; D055503:Protein Multimerization
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C411989:CikA protein, bacteria