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ATPase activity and its temperature compensation of the cyanobacterial clock protein KaiC
Author(s) -
Murakami Reiko,
Miyake Ayumi,
Iwase Ryo,
Hayashi Fumio,
Uzumaki Tatsuya,
Ishiura Masahiro
Publication year - 2008
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2008.01174.x
Subject(s) - biology , circadian clock , protein subunit , atpase , phosphorylation , random hexamer , biochemistry , microbiology and biotechnology , cyanobacteria , bacteria , enzyme , genetics , gene
KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria. KaiC is a homohexamer; its subunit contains duplicated halves, each with a set of ATPase motifs. Here, using highly purified KaiC preparations of the thermophilic cyanobacterium Thermosynechococcus elongatus BP‐1 produced in Escherichia coli , we found that the N‐ and C‐terminal domains of KaiC had extremely weak ATPase activity. ATPase activity showed temperature compensation in wild‐type KaiC, but not in KaiC S431A/T432A , a mutant that lacks two phosphorylation sites. We concluded that KaiC phosphorylation is involved in the ATPase temperature‐compensation mechanism—which is probably critical to the stability of the circadian clock in cyanobacteria—and we hypothesized the following temperature‐compensation mechanism: (i) The C‐terminal phosphorylation sites of a KaiC hexamer subunit are phosphorylated by the C‐terminal domain of an adjacent KaiC subunit; (ii) the phosphorylation suppresses the ATPase activity of the C‐terminal domain; and (iii) the phosphorylated KaiC spontaneously dephosphorylates, resulting in the recover of ATPase activity.