A unified scheme for carbon and electron flow coupled to ATP synthesis by substrate-level phosphorylation in the methanogenic bacteria

AbstractDue primarily to considerations of the nature of the electron transfer reactions which drive ATP synthesis in the methanogenic bacteria, substrate-level phosphorylation (SLP) has been generally ruled out. Recent studies, however, have cast doubt on an obligatory role for a transmembrane ion gradient in coupling. In this paper, a scheme is proposed for SLP coupled to methane formation. The essential features are phosphorylation of bound C1 intermediate coupled to intermolecular electron transfer in a multifunctional protein complex containing a collection of bound C1 and electron carriers. ATP synthesis is accomplished by subsequent phosphoryl transfer. The scheme is analogous to all known mechanisms of SLP and is compatible with most of the data published to date