Exchange of ADP with ATP in the CII ATPase domain promotes autophosphorylation of cyanobacterial clock protein KaiC.

ABSTRACT: The cyanobacterial circadian oscillator can be reconstituted in vitro. In the presence of KaiA and KaiB, the phosphorylation state of KaiC oscillates with a periodicity of ∼24 h. KaiC is a hexameric P-loop ATPase with autophosphorylation and autodephosphorylation activities. Recently, we found that dephosphorylation of KaiC occurs via reversal of the phosphorylation reaction: a phosphate group attached to Ser431/Thr432 is transferred to KaiC-bound ADP to generate ATP, which is subsequently hydrolyzed. This unusual reaction mechanism suggests that the KaiC phosphorylation rhythm is sustained by periodic shifts in the equilibrium of the reversible autophosphorylation reaction, the molecular basis of which has never been elucidated. Because KaiC-bound ATP and ADP serve as substrates for the f

SUBMITTER: Nishiwaki-Ohkawa T 

PROVIDER: S-EPMC3970490 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature