Studies on energy and electron transfer systems in green photosynthetic bacterium Chloropseudomonas ethylica strain 2K. I. Isolation and characterization of cytochromes from Chloropseudomonas ethylica strain 2K.

Abstract

Two cytochromes of the C-type, c-551.5 and c-555(550), were isolated from the soluble fraction of a green photosynthetic bacterium, Chloropseudomonas ethylica strain 2K, and highly purified by DEAE-cellulose and Amberlite CG-50 ion exchanger column chromatography. Cytochrome c-551.5 has absorption maxima at 551.5, 523 and 418nm in the reduced state and at 528, 408 and 351 nm in the oxidized state. This cytochrome is an auto-oxidizable, slightly basic protein having an isoelectric point of 7.77. It has a low mid-point redox potential of −209 mV at pH 7.0. The molecular weight of this protein is close to 11,500 and it contains two heme c groups per molecule of protein. These results indicate that cytochrome c-551.5 closely resembles cytochrome c8 from Desulfovibrio vulgaris (strain Hildenborough). Cytochrome c-555(550) has absorption maxima at 555, 523 and 417.5 nm in the reduced state and at 525, 412 and 358 nm in the oxidized state. This protein is very acidic, having an isoelectric point of 4.65. It has a mid-point redox potential of +103mV at pH 7.0. Its molecular weight is approximately 12,000. Cytochrome c-555(550) is similar to algal and higher plant f-type cytochromes except for redox potential. There is no evidence for the presence of a B-type cytochrome in Cps. ethylica strain 2K.