The partial resolution and dye-mediated reconstitution of methanol oxidase activity inMethylophilus methylotrophus

Abstract

Methylophilus methylotrophus is a methylotrophic bacterium which uses methanol as its preferred source of carbon and energy. In common with other methylotrophic bacteria it oxidises methanol to formaldehyde via a methanol dehydrogenase which contains a pyrrolo-quinoline quinone prosthetic group [1]. Subsequent electron transfer to oxygen occurs via an apparently relatively simple respiratory chain which is composed of one or more c-type cytochromes (c n a n d / o r cL) plus cytochrome oxidases o a n d / o r aa 3 [2-4]. The overall methanol oxidase system in M. methyl otrophus, as in other methylotrophs, has been shown to catalyse effective proton translocation [4-6] and hence to generate a protonmotive force which can subsequently drive ATP synthesis (M.J. Dawson and C.W. Jones, unpublished). This paper reports that the methanol dehydrogenase and a large proportion of the cytochrome c of M. methylotrophus is probably loosely bound to the periplasmic side of the respiratory membrane, whereas the cytochrome oxidases and the remainder of the cytochrome c are firmly membranebound. Methanol oxidase activity can be fully reconstituted from a mixture of periplasm and