Phylogenetic studies of two rubredoxins from sulfate reducing bacteria

The sequences of two rubredoxins isolated from the sulfate reducing bacteria: Desulfovibrio vulgaris and Desulfovibrio gigas have been elucidated. They have similar sequences but many more differences occur than would be expected from two bacteria of the same genus. Of the 52 sites, only 37 are occupied by identical residues. The primary structures are compared with those of the anaerobic bacteria rubredoxins of Clostridium pasteurianum, Micrococcus aerogenes, Pseudomonas oleovorans and Peptostreptococcus elsdenii: only 12 identities are found, mostly in the two clusters that contain two iron-bound cysteines each. A phylogenetic tree based on the primary structures is presented and possible relations with plant and bacterial ferredoxins are discussed. A secondary and tertiary structure stereochemically compatible with the sequence data, is proposed.