A PUTATIVE CYTOCHROME-C BIOGENESIS GENE IN SYNECHOCYSTIS SP PCC-6803

A gene (orf334) with homology to chloroplast ycf5 (ccsA) was isolated from the cyanobacterium Synechocystis PCC 6803. The mRNA level of orf3 34 decreases in the dark and increases rapidly upon illumination. Tran scription is initiated 69 nucleotides upstream of the start site of tr anslation. The deduced amino acid sequence of orf334 has limited ident ity with bacterial proteins involved in cytochrome c biogenesis. Seque nce comparison indicates differing pathways of cytochrome c biogenesis in cyanobacteria/chloroplasts and Gram(-) positive bacteria versus pr oteobacteria and mitochondria. Insertional inactivation of the orf334 gene gave rise to a heterozygous mutant, i.e. complete absence of the orf334 product seems to be lethal to the cell. (C) 1997 Federation of European Biochemical Societies.