4IJM

Crystal structure of circadian clock protein KaiC A422V mutant

Summary for 4IJM

• Entry DOI: 10.2210/pdb4ijm/pdb
• Related: 3DVL
• Descriptor: Circadian clock protein kinase KaiC, MAGNESIUM ION, ADENOSINE-5'-TRIPHOSPHATE, ... (5 entities in total)
• Functional Keywords: atp binding, biological rhythms, auto-kinase, phosphorylation, serine/threonine-protein kinase, transcription regulation, kaia, kaib, sasa, circadian clock protein, transferase
• Biological source: Synechococcus elongatus
• Total number of polymer chains: 6
• Total formula weight: 352881.48

Authors

Egli, M.,Pattanayek, R. (deposition date: 2012-12-21, release date: 2013-02-13, Last modification date: 2024-11-20)

Primary citation

Egli, M.,Pattanayek, R.,Sheehan, J.H.,Xu, Y.,Mori, T.,Smith, J.A.,Johnson, C.H.
Loop-Loop Interactions Regulate KaiA-Stimulated KaiC Phosphorylation in the Cyanobacterial KaiABC Circadian Clock.
Biochemistry, 52:1208-1220, 2013

PubMed Abstract: The Synechococcus elongatus KaiA, KaiB, and KaiC proteins in the presence of ATP generate a post-translational oscillator that runs in a temperature-compensated manner with a period of 24 h. KaiA dimer stimulates phosphorylation of KaiC hexamer at two sites per subunit, T432 and S431, and KaiB dimers antagonize KaiA action and induce KaiC subunit exchange. Neither the mechanism of KaiA-stimulated KaiC phosphorylation nor that of KaiB-mediated KaiC dephosphorylation is understood in detail at present. We demonstrate here that the A422V KaiC mutant sheds light on the former mechanism. It was previously reported that A422V is less sensitive to dark pulse-induced phase resetting and has a reduced amplitude of the KaiC phosphorylation rhythm in vivo. A422 maps to a loop (422-loop) that continues toward the phosphorylation sites. By pulling on the C-terminal peptide of KaiC (A-loop), KaiA removes restraints from the adjacent 422-loop whose increased flexibility indirectly promotes kinase activity. We found in the crystal structure that A422V KaiC lacks phosphorylation at S431 and exhibits a subtle, local conformational change relative to wild-type KaiC. Molecular dynamics simulations indicate higher mobility of the 422-loop in the absence of the A-loop and mobility differences in other areas associated with phosphorylation activity between wild-type and mutant KaiCs. The A-loop-422-loop relay that informs KaiC phosphorylation sites of KaiA dimer binding propagates to loops from neighboring KaiC subunits, thus providing support for a concerted allosteric mechanism of phosphorylation.

PubMed: 23351065
DOI: 10.1021/bi301691a

Experimental method

X-RAY DIFFRACTION (3.352 Å)