Evidence for a role of ClpP in the degradation of the chloroplast cytochrome b(6)f complex.
In the green alga Chlamydomonas reinhardtii, the ClpP protease is encoded by an essential chloroplast gene. Mutating its AUG translation initiation codon to AUU reduced ClpP accumulation to 25 to 45% of that of the wild type. Both the mature protein and the putative precursor containing its insertion sequence were present in reduced amounts. Attenuation of ClpP did not affect growth rates under normal conditions but restricted the ability of the cells to adapt to elevated CO(2) levels. It also affected the rate of degradation of the cytochrome b(6)f complex of the thylakoid membrane in two experimental situations: (1) during nitrogen starvation, and (2) in mutants deficient in the Rieske iron-sulfur protein. The ClpP level also controls the steady state accumulation of a mutated version of the Rieske protein. In contrast, attenuation of ClpP did not rescue the fully unassembled subunits in other cytochrome b(6)f mutants. We conclude that proteolytic disposal of fully or partially assembled cytochrome b(6)f is controlled by the Clp protease.
Majeran
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W
Centre National de la Recherche Scientifique (CNRS) UPR 1261, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France.
Wollman
F A
FA
Vallon
O
O
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000913:Antibodies, Protozoan; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D018387:Codon, Initiator / Q000235:genetics; D003573:Cytochrome b Group / Q000235:genetics / Q000378:metabolism*; D045346:Cytochrome b6f Complex; D017931:DNA Primers / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D014450:Electron Transport Complex III; D049071:Endopeptidase Clp; D004926:Escherichia coli / Q000235:genetics; D017125:Genes, Protozoan; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D011817:Rabbits; D012697:Serine Endopeptidases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014170:Transformation, Genetic
D000913:Antibodies, Protozoan; D018387:Codon, Initiator; D003573:Cytochrome b Group; D017931:DNA Primers; D016054:DNA, Protozoan; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D045346:Cytochrome b6f Complex; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; D014450:Electron Transport Complex III; D009584:Nitrogen