Circadian clock oscillator protein KaiB

UniProtKB accession:  Q79PF5

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UniProtKB description:  Key component of the KaiABC oscillator complex, which constitutes the main circadian regulator in cyanobacteria (PubMed:28302852, PubMed:9727980, PubMed:17717528). Complex composition changes during the circadian cycle to control KaiC phosphorylation. KaiA stimulates KaiC autophosphorylation, while KaiB sequesters KaiA, leading to KaiC autodephosphorylation. KaiA binding to the KaiC CII domain yields KaiA(2-4):KaiC(6) complexes which stimulate KaiC autophosphorylation. Phospho-Ser-431 KaiC accumulation triggers binding of KaiB to form the KaiB(6):KaiC(6) complex, leading to changes in the output regulators CikA and SasA. KaiB switches to a thioredoxin-like fold (KaiB(fs)) in complex with KaiC (PubMed:28302852, PubMed:26113641, PubMed:28302851). KaiB(6):KaiC(6) formation exposes a site for KaiA binding that sequesters KaiA from the CII domain, making the KaiC(6):KaiB(6):KaiA(12) complex that results in KaiC autodephosphorylation (PubMed:17717528, PubMed:17916691, PubMed:28302852). Complete dephosphorylation of KaiC leads to dissociation of KaiA(2):KaiB(1), completing 1 cycle of the Kai oscillator (PubMed:28302852).