Crystal structure of the redox-active cofactor dibromothymoquinone bound to circadian clock protein KaiA and structural basis for dibromothymoquinone's ability to prevent stimulation of KaiC phosphorylation by KaiA.

ABSTRACT: KaiA protein that stimulates KaiC phosphorylation in the cyanobacterial circadian clock was recently shown to be destabilized by dibromothymoquinone (DBMIB), thus revealing KaiA as a sensor of the plastoquinone (PQ) redox state and suggesting an indirect control of the clock by light through PQ redox changes. Here we show using X-ray crystallography that several DBMIBs are bound to KaiA dimer. Some binding modes are consistent with oligomerization of N-terminal KaiA pseudoreceiver domains and/or reduced interdomain flexibility. DBMIB bound to the C-terminal KaiA (C-KaiA) domain and limited stimulation of KaiC kinase activity by C-KaiA in the presence of DBMIB demonstrate that the cofactor may weakly inhibit KaiA-KaiC binding.

SUBMITTER: Pattanayek R 

PROVIDER: S-EPMC3561481 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature