Article
- The EMBO Journal (2005) 24, 1202 - 1210
- doi:10.1038/sj.emboj.7600606
Published online: 10 March 2005
Subject Categories:
LdpA: a component of the circadian clock senses redox state of the cell
Natalia B Ivleva1, Matthew R Bramlett2, Paul A Lindahl2 and Susan S Golden1
- Department of Biology, Texas A&M University, College Station, TX, USA
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA
Correspondence to:
Susan S Golden, Department of Biology, Texas A&M University, Biological Sciences Building, East, Room 314C, College Station, TX 77843-3258, USA. Tel.: +1 979 845 9824; Fax: +1 979 862 7659; E-mail: sgolden@tamu.edu
Received 19 August 2004; Accepted 9 February 2005
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.
Keywords:
- circadian clock,
- cyanobacteria,
- LdpA,
- protein interaction,
- redox
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