Isolation and properties of membrane-bound cytochrome c-552 from photosynthetic bacterium Chromatium vinosum

Abstract

A membrane-bound cytochrome c-552 was isolated and purified from the photosynthetic bacterium Chromatium vinosum by treatment with sodium cholate, sodium deoxycholate and bacterial alkaline protease followed by gel filtration.The purified cytochrome c-552, which may have been modified by the protease treatment, was electrophoretically homogeneous. Its minimal molecular weight was estimated to be 19 and 20 kdaltons, respectively by SDS polyacrylamide gel electrophoresis and by gel filtration on Sephadex G-100.Cytochrome c-552 showed the absorption maxima at 419, 523 and 552 nm in the reduced form. Reduced-minus-oxidized difference millimolar absorption coefficient was 10.6 for the wavelength pair, 552 minus 540 nm. The midpoint potential at pH 8.0 was -130 mV. The polarity in the amino acid composition of cytochrome c-552 was 40.1% and reflected its hydrophobicity.The solubilized cytochrome c-552 was shown to be a different entity from the soluble flavocytochrome c-552 in several respects.

The presence of cytochrome c1 in the purple sulfur bacterium Chromatium vinosum

“…c in this fraction. As C. vinosum chromatophores are known to contain a low potential (Em = + 10 mV) cytochrome c-552 [17,32-351, the midpoint potential of which can be lowered to -130 mV on removal from the membrane [35], no further attempt was made to characterize the lower potential cytochrome(s) of the octylglucoside-solubilized fraction. Rather an attempt was made to further characterize the newly discovered, high potential cyt.…”

“…Previous work [35] assignthat of cytochrome cl of mitochondria [3,36] and ed 23 kDa and 40 kDa to C. vinosum chromatophotosynthetic purple non-sulfur bacteria [8-131.…”

“…The presence of three heme-staining bands after SDS-PAGE separation of a C. vinosum chromatophore membrane fraction enriched in cytochrome suggests the presence of at least one additional cytochrome. The data in [35] ( fig.5) also suggests the presence of a 31 kDa, heme-containing protein in C. vinosum chromatophores although they did not comment on the significance of this component in their SDS-PAGE gels. The presence of a hydroquinonereducible component in C. vinosum chromatophores with absorbance maxima at 552-553, 523 and 422 nm also points to the presence of a previously undetected high-potential c-type cytochrome.…”

Purification, redox and spectroscopic properties of the tetraheme cytochrome c isolated from Rubrivivax gelatinosus

“…Several earlier reports on tetraheme cytochrome c preparations isolated from Chromatium vinosum , Thiocapsa pfennigii and Ecthiorhodospira species claimed that the high‐potential hemes were lost when the cytochrome was extracted from the membranes [41–43]. At that time, these hemes have been considered as components of a diheme cytochrome.…”

Photoreaction center of Ectothiorhodospira sp. Pigment, heme, quinone, and polypeptide composition

“…Recently, a c-552 preparation was obtained from chromatophores of Chr. vinosum by the combined action of detergent and protease (Doi et al, 1983). It had a molecular weight of 20 000 and was free both of the photoreaction center and of c-555.…”