title: Ccs1, a nuclear gene required for the post-translational assembly of chloroplast c-type cytochromes.
abstract: Nuclear genes play important regulatory roles in the biogenesis of the photosynthetic apparatus of eukaryotic cells by encoding factors that control steps ranging from chloroplast gene transcription to post-translational processes. However, the identities of these genes and the mechanisms by which they govern these processes are largely unknown. By using glass bead-mediated transformation to generate insertional mutations in the nuclear genome of Chlamydomonas reinhardtii, we have generated four mutants that are defective in the accumulation of the cytochrome b6f complex. One of them, strain abf3, also fails to accumulate holocytochrome c6. We have isolated a gene, Ccs1, from a C. reinhardtii genomic library that complements both the cytochrome b6f and cytochrome c6 deficiencies in abf3. The predicted protein product displays significant identity with Ycf44 from the brown alga Odontella sinensis, the red alga Porphyra purpurea, and the cyanobacterium Synechocystis strain PCC 6803 (25-33% identity). In addition, we note limited sequence similarity with ResB of Bacillus subtilis and an open reading frame in a homologous operon in Mycobacterium leprae (11-12% identity). On the basis of the pleiotropic c-type cytochrome deficiency in the ccs1 mutant, the predicted plastid localization of the protein, and its relationship to candidate cytochrome biosynthesis proteins in Gram-positive bacteria, we conclude that Ccs1 encodes a protein that is required for chloroplast c-type holocytochrome formation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: K
authors.initials: K
authors.lastname: Inoue
authors.forename: B W
authors.initials: BW
authors.lastname: Dreyfuss
authors.forename: K L
authors.initials: KL
authors.lastname: Kindle
authors.forename: D B
authors.initials: DB
authors.lastname: Stern
authors.forename: S
authors.initials: S
authors.lastname: Merchant
authors.forename: O A
authors.initials: OA
authors.lastname: Sodeinde
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism*; D003573:Cytochrome b Group / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D045346:Cytochrome b6f Complex; D003574:Cytochrome c Group / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins; D012150:Polymorphism, Restriction Fragment Length; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: C109655:Ccs1 protein, Chlamydomonas reinhardtii; D060365:Chloroplast Proteins; D003573:Cytochrome b Group; D003574:Cytochrome c Group; D009687:Nuclear Proteins; D010940:Plant Proteins; D015800:Protozoan Proteins; C075103:ccsA protein, protozoan; D045346:Cytochrome b6f Complex