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Structures of the cyanobacterial circadian oscillator frozen in a fully assembled state

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Science  17 Mar 2017:
Vol. 355, Issue 6330, pp. 1181-1184
DOI: 10.1126/science.aag3218

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Molecular clockwork from cyanobacteria

The cyanobacterial circadian clock oscillator can be reconstituted in a test tube from just three proteins—KaiA, KaiB, and KaiC—and adenosine triphosphate (ATP). Tseng et al. studied crystal and nuclear magnetic resonance structures of complexes of the oscillator proteins and their signaling output proteins and tested the in vivo effects of structure-based mutants. Large conformational changes in KaiB and ATP hydrolysis by KaiC are coordinated with binding to output protein, which couples signaling and the day-night transitions of the clock. Snijder et al. provide complementary analysis of the oscillator proteins by mass spectrometry and cryo–electron microscopy. Their results help to explain the structural basis for the dynamic assembly of the oscillator complexes.

Science, this issue p. 1174, p. 1181