The cytochrome subunit structure in the photosynthetic reaction center of Chromatium minutissimum

FEBS Letters

Rubin, A.B¹  Zakharova, N.I¹  Chamorovsky, S.K¹  Remennikov, S.M¹  Sabo, Ya² 

[1] Department of Biophysics, Biological Faculty, Lomonosov State University, Moscow 119899, Russia;Institute of Experimental Physics, Slovakian Academy of Sciences, Kosice, Slovakia

关键词: Photosynthetic bacterium;    Reaction center;    Cytochrome;    Chromatium minutissimum;   

DOI  :  10.1016/S0014-5793(98)00013-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Gel-electrophoretic assay revealed that the photosynthetic reaction center (RC) of Chromatium minutissimum, in contrast to the well-known RC Rhodopseudomonas viridis, consists of five rather than four subunits with molecular masses of 37, 34, 25, 19, and 17 kDa. The 37- and 19-kDa subunits are stained with tetramethylbenzidine for the cytochrome c hemes. Absorption spectra show that the concentration of reduced cytochromes in the C. minutissimum RC poised at redox potential of −150 mV (fully reduced pool of hemes) is about three times more than in the C. minutissimum RC poised at redox potential of +260 mV (only high-potential hemes are reduced). The results of redox titration of absorption changes at the cytochrome c α-band are most appropriately approximated by a six-component theoretical curve with the midpoint potentials of E _m1=390 mV, E _m2=320 mV, E _m3=210 mV, E _m4=100 mV, E _m5=20 mV, and E _m6=−50 mV. Possible functions of the cytochromes with the midpoint potentials 210 and 100 mV, which have not been found in purple bacteria before, are discussed.

【 授权许可】

Unknown