Amino acid sequence and function of rubredoxin from Desulfovibrio vulgaris Miyazaki

Rubredoxin was purified from Desulfovibrio vulgaris Miyazaki. It was sequenced and some of its properties determined. Rubredoxin is composed of 52 amino acids. It is highly homologous to that from D. vulgaris Hildenborough. Its N-terminal methionyl residue is partially formylated. The millimolar absorption coefficients of the rubredoxin at 489 nm and 280 nm are 8.1 and 18.5, respectively, and the standard redox potential is +5 mV, which is slightly higher than those of other rubredoxins. Rubredoxin, as well as cytochrome c-553, was reduced with lactate by the action of lactate dehydrogenase of this organism, and the reaction was stimulated with 2-methyl-1,4-naphthoquinone. It is suggested that rubredoxin, in collaboration with membranous quinone, functions as a natural electron carrier for cytoplasmic lactate dehydrogenase of this organism, whereas cytochrome c-553 plays the same role for periplasmic lactate dehydrogenase.