title: Functional analysis of a divergent system II protein, Ccs1, involved in c-type cytochrome biogenesis.
abstract: The Ccs1 gene, encoding a highly divergent novel component of a system II type c-type cytochrome biogenesis pathway, is encoded by the previously defined CCS1 locus in Chlamydomonas reinhardtii. phoA and lacZalpha bacterial topological reporters were used to deduce a topological model of the Synechocystis sp. 6803 Ccs1 homologue, CcsB. CcsB, and therefore by analogy Ccs1, possesses a large soluble lumenal domain at its C terminus that is tethered in the thylakoid membrane by three closely spaced transmembrane domains in the N-terminal portion of the protein. Molecular analysis of ccs1 alleles reveals that the entire C-terminal soluble domain is essential for Ccs1 function and that a stromal loop appears to be important in vivo, at least for maintenance of Ccs1. Site-directed mutational analysis reveals that a single histidine (His(274)) within the last transmembrane domain, preceding the large lumenal domain, is required for c-type cytochrome assembly, whereas an invariant cysteine residue (Cys(199)) is shown to be non-essential. Ccs1 is proposed to interact with other Ccs components based on its reduced accumulation in ccs2, ccs3, ccs4, and ccsA strains.
authors.affiliation: Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095-1569, USA.
authors.forename: Beth Welty
authors.initials: BW
authors.lastname: Dreyfuss
authors.forename: Patrice P
authors.initials: PP
authors.lastname: Hamel
authors.forename: Stacie S
authors.initials: SS
authors.lastname: Nakamoto
authors.forename: Sabeeha
authors.initials: S
authors.lastname: Merchant
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D002462:Cell Membrane / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000378:metabolism; D060365:Chloroplast Proteins; D003580:Cytochromes / Q000378:metabolism*; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D006639:Histidine / Q000737:chemistry; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010940:Plant Proteins; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D012313:RNA / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism; D013997:Time Factors
chemical_list: C109655:Ccs1 protein, Chlamydomonas reinhardtii; D060365:Chloroplast Proteins; D003580:Cytochromes; D010940:Plant Proteins; D015800:Protozoan Proteins; D006639:Histidine; D012313:RNA