Cytochrome pigments from the green photosynthetic bacterium Chlorobium thiosulphatophilum

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Abstract
Two cytochrome pigments with widely differentisoelectricpoints were separated from extracts of C. thiosulphatophilum; the basic pigment, obtained in a homogeneous state, has absorption maxima in the reduced form at 554, 523 and 417 mu, is not auto-oxidizable and forms compounds with nitric oxide, when in the oxidized state, but not with cyanide or carbon monoxide when oxidized or reduced. The Eq value is 140 mv. The prosthetic group is closely related to that of cytochrome c. The molecular weight is about 12,000 and there is one haem group per molecule. The acidic pigment, the best preparation of which still contained about 27% of colourless impurity, has absorption maxima in the reduced form at 553, 522 and 417 m[mu], and resembles the basic pigment in general properties. The Eq value is 163 mv. The molecular weight is 45,000-75 000 from the ultracentrifuge study and the maximum molecular weight is about 50 000 from the haem content. These pigments together account for up to 0.5% of the dry weight of the bacteria. No other haem compounds were detected in significant amounts.