title: Protein-Protein Interactions in the Cyanobacterial Circadian Clock: Structure of KaiA Dimer in Complex with C-Terminal KaiC Peptides at 2.8 Å Resolution.
abstract: In the cyanobacterial circadian clock, the KaiA, -B, and -C proteins with ATP constitute a post-translational oscillator. KaiA stimulates the KaiC autokinase, and KaiB antagonizes KaiA action. KaiA contacts the intrinsically disordered C-terminal regions of KaiC hexamer to promote phosphorylation across subunit interfaces. The crystal structure of KaiA dimer from Synechococcus elongatus with two KaiC C-terminal 20mer peptides bound reveals that the latter adopt an α-helical conformation and contact KaiA α-helical bundles via mostly hydrophobic interactions. This complex and the crystal structure of KaiC hexamer with truncated C-terminal tails can be fit into the electron microscopy (EM) density of the KaiA:KaiC complex. The hybrid model helps rationalize clock phenotypes of KaiA and KaiC mutants.
authors.affiliation: Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: Rekha
authors.initials: R
authors.lastname: Pattanayek
authors.affiliation: Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: Martin
authors.initials: M
authors.lastname: Egli
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D046940:Synechococcus / Q000737:chemistry* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D010455:Peptides