Hyphomicrobium X, grown on methanol with O2 or nitrate as electron acceptor, contains two major soluble cytochromes c. These were isolated in electrophoretically homogeneous form. They are related to cytochromes c already described for other methylotrophic bacteria and designated cytochromes cH and cL (properties indicated in that order) in view of the following characteristics: absorption maxima of the reduced forms (414, 520 and 551 nm and 414, 520 and 550 nm); molar absorption coefficients of the alpha-bands (23,700 M-1.cm-1 and 21,600 M-1.cm-1); maxima of the alpha-bands (no splitting) at 77 K (547.6 nm and 548.5 nm); Mr values of the native proteins (15,000 and 19,500); pI values (7.4 and 7.5, and 4.3); midpoint potentials at pH 7.0 (+292 mV and +270 mV). Both were monomers containing 1 haem c group per protein molecule, the oxidized forms binding cyanide at high pH. Autoreduction also occurred at high pH but at a rate significantly lower than that reported for other ferricytochromes c. On the other hand, the reverse situation applies to the reduction of ferricytochrome cL by reduced methanol dehydrogenase, the reduction occurring instantaneously at pH 7 but much more slowly at pH 9 (ferricytochrome cH was reduced at a 7-fold lower rate, but the rates at pH 7 and 9 were similar). Insignificant reduction was observed with cyclopropanol-inactivated enzyme or with enzyme in the presence of EDTA. In view of the dissimilarities, it is concluded that different mechanisms operate in the autoreduction of ferricytochrome cL and in its reduction by reduced methanol dehydrogenase.
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Research Article|
April 15 1988
The soluble cytochromes c of methanol-grown Hyphomicrobium X. Evidence against the involvement of autoreduction in electron-acceptor functioning of cytochrome cL
M Dijkstra
;
M Dijkstra
Laboratory of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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J Frank, Jzn
;
J Frank, Jzn
Laboratory of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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J E van Wielink
;
J E van Wielink
Laboratory of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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J A Duine
J A Duine
Laboratory of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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Biochem J (1988) 251 (2): 467–474.
Citation
M Dijkstra, J Frank, J E van Wielink, J A Duine; The soluble cytochromes c of methanol-grown Hyphomicrobium X. Evidence against the involvement of autoreduction in electron-acceptor functioning of cytochrome cL. Biochem J 15 April 1988; 251 (2): 467–474. doi: https://doi.org/10.1042/bj2510467
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