title: Biochemical evidence for a timing mechanism in prochlorococcus.
abstract: Organisms coordinate biological activities into daily cycles using an internal circadian clock. The circadian oscillator proteins KaiA, KaiB, and KaiC are widely believed to underlie 24-h oscillations of gene expression in cyanobacteria. However, a group of very abundant cyanobacteria, namely, marine Prochlorococcus species, lost the third oscillator component, KaiA, during evolution. We demonstrate here that the remaining Kai proteins fulfill their known biochemical functions, although KaiC is hyperphosphorylated by default in this system. These data provide biochemical support for the observed evolutionary reduction of the clock locus in Prochlorococcus and are consistent with a model in which a mechanism that is less robust than the well-characterized KaiABC protein clock of Synechococcus is sufficient for biological timing in the very stable environment that Prochlorococcus inhabits.
authors.affiliation: Institute for Theoretical Biology, Humboldt University, Berlin, Germany. ilka.axmann@charite.de
authors.forename: Ilka M
authors.initials: IM
authors.lastname: Axmann
authors.forename: Ulf
authors.initials: U
authors.lastname: Dühring
authors.forename: Luiza
authors.initials: L
authors.lastname: Seeliger
authors.forename: Anne
authors.initials: A
authors.lastname: Arnold
authors.forename: Jens T
authors.initials: JT
authors.lastname: Vanselow
authors.forename: Achim
authors.initials: A
authors.lastname: Kramer
authors.forename: Annegret
authors.initials: A
authors.lastname: Wilde
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D048929:Prochlorococcus / Q000502:physiology*; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria