KaiB domain (IPR011649)

Short name: KaiB_domain

Overlapping homologous superfamilies

Domain relationships



The cyanobacterial clock proteins KaiA, KaiB and SasA are proposed as regulators of the circadian rhythm in cyanobacteria [PMID: 12441347, PMID: 12727878]. Mutations in both proteins have been reported to alter or abolish circadian rhythmicity. KaiB adopts an alpha-beta meander motif and is found to be a dimer [PMID: 15313603]. KaiB was originally discovered from the cyanobacterium Synechococcus as part of the circadian clock gene cluster, kaiABC. KaiB attenuates KaiA-enhanced KaiC autokinase activity by interacting with KaiA-KaiC complexes in a circadian fashion [PMID: 15071498, PMID: 12727879]. KaiB is membrane-associated as well as cytosolic. The amount of membrane-associated protein peaks in the evening (at circadian time (CT) 12-16) while the cytosolic form peaks later (at CT 20). The rhythmic localization of KaiB may function in regulating the formation of Kai complexes. SasA is a sensory histidine kinase which associates with KaiC [PMID: 10786837]. Although it is not an essential oscillator component, it is important in enhancing kaiABC expression and is important in metabolic growth control under day/night cycle conditions. SasA contains an N-terminal sensory domain with a TRX fold which is involved in the SasA-KaiC interaction [PMID: 12449424]. This domain shows high sequence similarity with KaiB [PMID: 15014139]. However, the KaiB structure does not show a classical TRX fold. The N-terminal half of KaiB shares the same beta-alpha-beta topology as TRX, but the topology of its C-terminal half diverges.

GO terms

Biological Process

GO:0048511 rhythmic process

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.