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Science. 2017 Mar 17;355(6330):1174-1180. doi: 10.1126/science.aag2516. Epub 2017 Mar 16.

Structural basis of the day-night transition in a bacterial circadian clock.

Author information

1
Quantitative and Systems Biology, University of California, Merced, CA 95343, USA.
2
Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
3
School of Natural Sciences, University of California, Merced, CA 95343, USA.
4
Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.
5
Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA.
6
Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
7
Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
8
Quantitative and Systems Biology, University of California, Merced, CA 95343, USA. aliwang@ucmerced.edu cpartch@ucsc.edu.
9
Health Sciences Research Institute, University of California, Merced, CA 95343, USA.
10
Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA. aliwang@ucmerced.edu cpartch@ucsc.edu.

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.

Comment in

PMID:
28302851
PMCID:
PMC5441561
DOI:
10.1126/science.aag2516
[Indexed for MEDLINE]
Free PMC Article

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