title: Structural insights into a circadian oscillator.
abstract: An endogenous circadian system in cyanobacteria exerts pervasive control over cellular processes, including global gene expression. Indeed, the entire chromosome undergoes daily cycles of topological changes and compaction. The biochemical machinery underlying a circadian oscillator can be reconstituted in vitro with just three cyanobacterial proteins, KaiA, KaiB, and KaiC. These proteins interact to promote conformational changes and phosphorylation events that determine the phase of the in vitro oscillation. The high-resolution structures of these proteins suggest a ratcheting mechanism by which the KaiABC oscillator ticks unidirectionally. This posttranslational oscillator may interact with transcriptional and translational feedback loops to generate the emergent circadian behavior in vivo. The conjunction of structural, biophysical, and biochemical approaches to this system reveals molecular mechanisms of biological timekeeping.
authors.affiliation: Department of Biological Sciences, Box 35-1634, Vanderbilt University, Nashville, TN 37235-1634, USA. carl.h.johnson@vanderbilt.edu
authors.forename: Carl Hirschie
authors.initials: CH
authors.lastname: Johnson
authors.forename: Martin
authors.initials: M
authors.lastname: Egli
authors.forename: Phoebe L
authors.initials: PL
authors.lastname: Stewart
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001683:Biological Clocks; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000502:physiology; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins; D019281:Dimerization; D008958:Models, Molecular; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011487:Protein Conformation; D046940:Synechococcus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria