Disease relevance of ccsA

• Sequence analysis of the cloned ccsA and Ccs1 genes indicates that the predicted protein products are integral membrane proteins with homologues in cyanobacteria, some gram-positive bacteria (Bacillus subtilis, Mycobacterium spp.), beta-proteobacteria (Neisseria spp.) and an epsilon-proteobacterium (Helicobacter pylori) [1].

High impact information on ccsA

• Functional analysis of CcsA through site-directed mutagenesis enabled the designation of the initiation codon of the ccsA gene and established the functional importance of the WWD signature motif and the absolute requirement of all three histidines for the assembly of plastid c-type cytochromes [2].
• In a ccsA mutant, a 200-kDa Ccs1-containing complex is absent from solubilized thylakoid membranes, suggesting that CcsA operates together with Ccs1 [2].
• The complementing gene, renamed ccsA (for c-type cytochrome synthesis), is expressed in wild-type and B6 cells but is non-functional in B6 owing to an early frameshift mutation [3].
• B6 is unable to synthesize functional forms of cytochromes f and c6 owing to a chloroplast genome mutation that prevents heme attachment [3].
• We therefore investigated, by site-directed mutagenesis, the possible interplay between protein processing and heme attachment to cytochrome f in Chlamydomonas reinhardtii [4].

Biological context of ccsA

• For strains ct34 and ct59, where the phenotype displays uniparental inheritance, the mutations were localized to the chloroplast ccsA gene, which was shown previously to be required for heme attachment to chloroplast apocytochromes [5].

Associations of ccsA with chemical compounds

• A similar conclusion is reached from examination of cytochrome c6 synthesis in gabaculine-treated cells where inhibition of heme attachment did not prevent either of the two processing steps [6].
• Biochemical comparison of the proline-containing transformants with a cytochrome b6 mutant deficient in heme-attachment indicates that their primary defect is at the level of assembly of apocytochrome b6 with the bh heme, thereby preventing assembly of the whole cytochrome b6f complex [7].

Other interactions of ccsA

• Genetic analyses of Chlamydomonas reinhardtii ccs mutants, which are pleiotropically deficient in both the membrane-anchored cytochrome f and the soluble cytochrome c6, revealed a minimum of six loci, plastid ccsA and nuclear CCS1 through CCS5, that are required for the conversion of the chloroplast apocytochromes to their respective holo forms [1].

Analytical, diagnostic and therapeutic context of ccsA

• Sequence analysis of the ccsA gene in strain B6R indicates that it is a true revertant [3].

References