Open AccessAn arginine tetrad as mediator of input‐dependent and input‐independent ATPases in the clock protein KaiC
Author(s) -
Pattanayek Rekha,
Xu Yao,
Lamichhane Aashish,
Johnson Carl H.,
Egli Martin
Publication year - 2014
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s1399004714003228
Subject(s) - circadian clock , atpase , microbiology and biotechnology , biology , phosphorylation , dephosphorylation , biophysics , chemistry , circadian rhythm , biochemistry , phosphatase , enzyme , endocrinology
A post‐translational oscillator (PTO) composed of the proteins KaiA, KaiB and KaiC is at the heart of the cyanobacterial circadian clock. KaiC interacts with KaiA and KaiB over the daily cycle, and CII domains undergo rhythmic phosphorylation/dephosphorylation with a 24 h period. Both the N‐terminal (CI) and C‐terminal (CII) rings of KaiC exhibit ATPase activity. The CI ATPase proceeds in an input‐independent fashion, but the CII ATPase is subject to metabolic input signals. The crystal structure of KaiC from Thermosynechococcus elongatus allows insight into the different anatomies of the CI and CII ATPases. Four consecutive arginines in CI (Arg linker) that connect the P‐loop, CI subunits and CI and CII at the ring interface are primary candidates for the coordination of the CI and CII activities. The mutation of linker residues alters the period or triggers arhythmic behavior. Comparison between the CI and CII structures also reveals differences in loop regions that are key to KaiA and KaiB binding and activation of CII ATPase and kinase. Common packing features in KaiC crystals shed light on the KaiB–KaiC interaction.