Transmembrane electron transport in ascorbate‐loaded plasma membrane vesicles from higher plants involves a b‐type cytochrome

Abstract

The possible involvement of a high‐potential b‐type cytochrome in plasma membrane electron transport was tested using ascorbate‐loaded membrane vesicles. Absorption spectra demonstrated that the cytochrome was about 89% reduced in these preparations. Use of ascorbate oxidase and washing of the vesicles further indicated flat reduction was mediated by intra‐vesicular ascorbate. Addition of low concentrations of ferricyanide caused a rapid cytochrome oxidation followed by a slower re‐reduction. The Kinetics of this response indicate that the electron acceptor was fully reduced berore re‐reduction of the cytochrome occurred. These observations suggest that the b‐type cytochrome mediates transmembrane electron transfer.