Amino acid sequence of ferredoxin II from the phototroph Rhodospirillum rubrum: Characteristics of a 7Fe ferredoxin.

The complete sequence of amino acids of ferredoxin II (FdII) from Rhodospirillum rubrum was determined by repetitive Edman degradation using pyridylethylated-ferredoxin and oxidized, denatured ferredoxin. Peptides derived from trypsin, pepsin, Glu-C endoproteinase, Arg-C endoproteinase, tryptophan specific cleavage and partial acid hydrolysis and C-terminal sequence from carboxypeptidase digestion were used to construct the total sequence. RrFdII is a polypeptide of 104 amino acids having a calculated molecular weight of 11556 excluding the iron and sulfur atoms. The complete amino acid sequence was: PYVVTENCIKCKYQDCVEVCPVDCFYEGENFLVINPDECIDCGVCNPECPAEAIAGKWLEINRKFADLWPNITRKGPAL ADADDWKDKPDKTGLLSENPGKGTV. Sequence comparisons, EPR characteristics and iron analyses indicate that RrFdII has structural features in common with ferredoxins containing [3Fe-4S], [4Fe-4S] centers. Of 104 amino acids, 60 (58%) including all 9 cysteines, are found in identical locations in the 7Fe ferredoxin prototype, Azotobacter vinelandii FdI.