Characteristics and amino-acid composition of a c-type cytochrome in electron acceptor function during thiosulfate-linked photoautotrophic growth of Rhodopseudomonas palustris.

The purple bacterium Rhodopseudomonas palustris (Rhodospirillaceae) was grown in the light with thiosulfatee as the only electron source and HCO theta 3/CO2 as carbon requirement. During thiosulfat oxidation, photolithoautotrophically growing cells transferred the electrons enzymatically towards an endogenous, soluble cytochrome of type c. The cytochrome c in electron acceptor function was purified to homogeneity and appeared as a single protein band in a dodecyl sulfate disc gel electrophoresis. Its molecular mass was determined to be about 16000 Da and its pI value 10.0. The determination of its amino-acid composition revealed a long-chained cytochrome represented by more than 120 amino-acid residues with a characteristic content of lysine and a lack of tryptophan.