This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Google Scholar
Right arrow Articles by Chen, Y.
Right arrow Articles by Golden, S. S.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chen, Y.
Right arrow Articles by Golden, S. S.

 Previous Article  |  Next Article 

Journal of Bacteriology, July 2009, p. 4392-4400, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.00334-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Novel Allele of kaiA Shortens the Circadian Period and Strengthens Interaction of Oscillator Components in the Cyanobacterium Synechococcus elongatus PCC 7942{triangledown}

You Chen,1,{dagger} Yong-Ick Kim,2,{ddagger} Shannon R. Mackey,1,§ C. Kay Holtman,1 Andy LiWang,2,{ddagger} and Susan S. Golden1*

Department of Biology, Texas A&M University, College Station, Texas 77843-3258,1 Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843-21282

Received 10 March 2009/ Accepted 21 April 2009

The basic circadian oscillator of the unicellular fresh water cyanobacterium Synechococcus elongatus PCC 7942, the model organism for cyanobacterial circadian clocks, consists of only three protein components: KaiA, KaiB, and KaiC. These proteins, all of which are homomultimers, periodically interact to form large protein complexes with stoichiometries that depend on the phosphorylation state of KaiC. KaiA stimulates KaiC autophosphorylation through direct physical interactions. Screening a library of S. elongatus transposon mutants for circadian clock phenotypes uncovered an atypical short-period mutant that carries a kaiA insertion. Genetic and biochemical analyses showed that the short-period phenotype is caused by the truncation of KaiA by three amino acid residues at its C terminus. The disruption of a negative element upstream of the kaiBC promoter was another consequence of the insertion of the transposon; when not associated with a truncated kaiA allele, this mutation extended the circadian period. The circadian rhythm of KaiC phosphorylation was conserved in these mutants, but with some modifications in the rhythmic pattern of KaiC phosphorylation, such as the ratio of phosphorylated to unphosphorylated KaiC and the relative phase of the circadian phosphorylation peak. The results showed that there is no correlation between the phasing of the KaiC phosphorylation pattern and the rhythm of gene expression, measured as bioluminescence from luciferase reporter genes. The interaction between KaiC and the truncated KaiA was stronger than normal, as shown by fluorescence anisotropy analysis. Our data suggest that the KaiA-KaiC interaction and the circadian pattern of KaiC autophosphorylation are both important for determining the period, but not the relative phasing, of circadian rhythms in S. elongatus.

* Corresponding author. Mailing address: Division of Biological Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093. Phone: (858) 246-0658. Fax: (858) 534-7108. E-mail: sgolden{at}ucsd.edu

{triangledown} Published ahead of print on 24 April 2009.

{dagger} Present address: Synthetic Genomics Inc., 11149 North Torrey Pines Road, La Jolla, CA 92037.

{ddagger} Present address: School of Natural Sciences, University of California at Merced, 4225 N. Hospital Road, Atwater, CA 95301.

§ Present address: Biology Department, St. Ambrose University, 518 West Locust Street, Davenport, IA 52803.

Journal of Bacteriology, July 2009, p. 4392-4400, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.00334-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»