Nucleotide binding and autophosphorylation of the clock protein KaiC as a circadian timing process of cyanobacteria
AUTOR(ES)
Nishiwaki, Taeko
FONTE
The National Academy of Sciences
RESUMO
A negative feedback control of kaiC expression by KaiC protein has been proposed to generate a basic oscillation of the circadian clock in the cyanobacterium Synechococcus sp. PCC 7942. KaiC has two P loops or Walker's motif As, that are potential ATP-/GTP-binding motifs and DXXG motifs conserved in various GTP-binding proteins. Herein, we demonstrate that in vitro KaiC binds ATP and, with lower affinity, GTP. Point mutation by site-directed mutagenesis of P loop 1 completely nullified the circadian rhythm of kaiBC expression and markedly reduced ATP-binding activity. Moreover, KaiC can be autophosphorylated in vitro. These results suggest that the nucleotide-binding activity of KaiC plays important roles in the generation of circadian oscillation in cyanobacteria.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=26691Documentos Relacionados
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