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A sequential program of dual phosphorylation of KaiC as a basis for circadian rhythm in cyanobacteria
Author(s) -
Nishiwaki Taeko,
Satomi Yoshinori,
Kitayama Yohko,
Terauchi Kazuki,
Kiyohara Reiko,
Takao Toshifumi,
Kondo Takao
Publication year - 2007
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601832
Subject(s) - biology , circadian rhythm , cyanobacteria , rhythm , bacterial circadian rhythms , circadian clock , dual (grammatical number) , chronobiology , phosphorylation , microbiology and biotechnology , neuroscience , genetics , medicine , bacteria , art , literature
The circadian phosphorylation cycle of the cyanobacterial clock protein KaiC has been reconstituted in vitro . The phosphorylation profiles of two phosphorylation sites in KaiC, serine 431 (S431) and threonine 432 (T432), revealed that the phosphorylation cycle contained four steps: (i) T432 phosphorylation; (ii) S431 phosphorylation to generate the double‐phosphorylated form of KaiC; (iii) T432 dephosphorylation; and (iv) S431 dephosphorylation. We then examined the effects of mutations introduced at one KaiC phosphorylation site on the intact phosphorylation site. We found that the product of each step in the phosphorylation cycle regulated the reaction in the next step, and that double phosphorylation converted KaiC from an autokinase to an autophosphatase, whereas complete dephosphorylation had the opposite effect. These mechanisms serve as the basis for cyanobacterial circadian rhythm generation. We also found that associations among KaiA, KaiB, and KaiC result from S431 phosphorylation, and these interactions would maintain the amplitude of the rhythm.