Purification and characterization of two soluble cytochromes from the alkalophile Bacillus firmus RAB

Biochim Biophys Acta. 1988 May 11;933(3):470-7. doi: 10.1016/0005-2728(88)90082-5.


A soluble cytochrome c and soluble cytochrome b were purified from the alkalophilic Bacillus firmus RAB. The cytochrome c, with an alpha band at 552 nm, had an apparent molecular weight of 16,500 and was acidic, with a pI of 3.4. At both pH 7.0 and 8.3, the midpoint potential of c-552 was +66 mV. Above pH 8.3, the cytochrome exhibited a pH-dependent decrease in midpoint potential. This property, among others, distinguished the cytochrome c-552 from other membrane-associated c-type cytochromes. The soluble cytochrome b, with an alpha band maximum at 558 nm, had a molecular weight of approx. 15,500 and was also an acidic protein, with a pI of 3.07. It exhibited a pH-independent midpoint potential of +28 mV.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Bacillus / analysis*
  • Cell Membrane / metabolism
  • Chromatography, Gel
  • Cytochrome b Group / isolation & purification*
  • Cytochrome c Group / isolation & purification*
  • Electrophoresis, Polyacrylamide Gel
  • Hydrogen-Ion Concentration
  • Isoelectric Point
  • Molecular Weight
  • Oxidation-Reduction
  • Spectrophotometry


  • Amino Acids
  • Cytochrome b Group
  • Cytochrome c Group