CLONING AND SEQUENCE-ANALYSIS OF THE GENE ENCODING THE LOW POTENTIAL CYTOCHROME-C OF SYNECHOCYSTIS PCC-6803

The gene for the low potential cytochrome c (petK) was isolated from a genomic library of Synechocystis PCC 6803. The nucleotide sequence of this gene contains two regions with sequence similarity to two region s in the gene for the high potential cytochrome c(6) of the organism. The sixth iron ligand can be identified with a conserved histidine. Ex periments demonstrate the reduction of the low potential cytochrome by reduced ferredoxin II. The heme of the cytochrome is flanked by lysin es which may be involved in orienting the ferredoxin near the site of electron donation.