title: LdpA: a component of the circadian clock senses redox state of the cell.
abstract: The endogenous 24-h (circadian) rhythms exhibited by the cyanobacterium Synechococcus elongatus PCC 7942 and other organisms are entrained by a variety of environmental factors. In cyanobacteria, the mechanism that transduces environmental input signals to the central oscillator of the clock is not known. An earlier study identified ldpA as a gene involved in light-dependent modulation of the circadian period, and a candidate member of a clock-entraining input pathway. Here, we report that the LdpA protein is sensitive to the redox state of the cell and exhibits electron paramagnetic resonance spectra consistent with the presence of two Fe4S4 clusters. Moreover, LdpA copurifies with proteins previously shown to be integral parts of the circadian mechanism. We also demonstrate that LdpA affects both the absolute level and light-dependent variation in abundance of CikA, a key input pathway component. The data suggest a novel input pathway to the circadian oscillator in which LdpA is a component of the clock protein complex that senses the redox state of a cell.
authors.affiliation: Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
authors.forename: Natalia B
authors.initials: NB
authors.lastname: Ivleva
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Bramlett
authors.forename: Paul A
authors.initials: PA
authors.lastname: Lindahl
authors.forename: Susan S
authors.initials: SS
authors.lastname: Golden
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001683:Biological Clocks / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D056925:Circadian Rhythm Signaling Peptides and Proteins; D020868:Gene Silencing; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008027:Light; D010084:Oxidation-Reduction; D011494:Protein Kinases / Q000378:metabolism; D046940:Synechococcus / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007506:Iron-Sulfur Proteins; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; C015482:protein kinase modulator; D011494:Protein Kinases; C411989:CikA protein, bacteria