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Plant Physiology 68:658-663 (1981)
© 1981 American Society of Plant Biologists

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Optical and Potentiometric Study of the b- and c-Type Cytochromes in Mushroom Agaricus bisporus Lge Mitochondria

Michel Denis1 and Jean-Paul Gallinet2,3

1 Faculté des Sciences de Luminy, Case 901, Laboratoire de Physiologie Cellulaire, ERA 619, 13288 Marseille cédex 9, France, 2 Université Pierre et Marie Curie, Laboratoire de Biologie Végétale IV, 75005 Paris, France

Differential spectrometry revealed two species for the b-type, as well as for the c-type, cytochromes in mitochondria from Agaricus bisporus Lge. The two b-type components are denoted according to their peak position in the {alpha} region at room temperature, i.e. b560 and b566. The b556 component present in all the studied higher plant mitochondria was not detected in the system. At 293 K, the c-type cytochromes exhibit a common {alpha} band with a maximum at 550 nanometers. This band is split at 77 K, with peak positions at 547 nanometers (cytochrome c) and 552 nanometers (cytochrome c1).

Redox titrations, analyzed according to a new method (Denis, Neau, Blein 1980 Bioelectrochem Bioenerg 7: 757-773), also yielded the resolution of two species of b-type and c-type cytochromes. The b components have midpoint potential values at pH 7.2 and 20 C of Em1 = 40 ± 10 millivolts and Em2 = 175 ± 10 millivolts. Their calculated individual difference spectra exhibit {alpha} bands with identical maxima at 561 nanometers, in contrast with optical observations. The midpoint potential values of the resolved c components are 210 ± 10 millivolts and 292 ± 5 millivolts at pH 7.2 and 20 C. Their corresponding calculated difference spectra have their {alpha} band maxima at 553 and 551 nanometers. These two species have been identified respectively with cytochrome c1 and cytochrome c. The ratio of the maximum optical contributions, c/c1, is in the range 4/1 to 5/1, in contrast with other results related to yeast or higher plant mitochondria where it amounts to 2/1 or even 1.3/1.

3 Permanent address: Université de Franche-Comté, Laboratoire de Biologie Végétale, La Bouloie, Route de gray, 25030 Besançon Cedex, France.






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Copyright © 1981 by the American Society of Plant Biologists