Genetic analysis of chloroplast c-type cytochrome assembly in Chlamydomonas reinhardtii: One chloroplast locus and at least four nuclear loci are required for heme attachment.

摘要: Chloroplasts contain up to two c-type cytochromes, membrane-anchored cytochrome f and soluble c6. To elucidate the post-translational events required for their assembly, acetate-requiring mutants of Chlamydomonas reinhardtii that have combined deficiencies in both plastid-encoded nucleus-encoded c6 been identified analyzed. For strains ct34 ct59, where phenotype displays uniparental inheritance, mutations were localized chloroplast ccsA gene, which was shown previously be heme attachment apocytochromes. The another eight nuclear genome. Complementation tests these plus three same (ac206, F18, F2D8) indicate 11 ccs define four loci, CCS1-CCS4. We conclude products CCS1-CCS4 loci are not translocation or processing preproteins but, like CcsA, they step during assembly holocytochrome gene is transcribed each mutants, but its protein product absent ccs1 it appears degradation susceptible ccs3 ccs4 strains. suggest Ccsl may associated with CcsA a multisubunit "holocytochrome c complex," we hypothesize other CCS correspond subunits.