Phosphorylative Electron Transport Without Quinone

Abstract

The respiratory quinones are considered as essential components of bacterial and mitochondrial phosphorylative electron transport (Kröger 1977; Kröger et al. 1986). They serve as diffusible redox mediators between membrane-integrated dehydrogenases and electron transfer complexes such as the cytochrome b/c₁- complex, or certain reductases which react with O₂ or other terminal acceptors. In addition, quinones are postulated to be involved in the generation of the electrochemicalproton potential (Δ$\tilde{\mu}$ _H) across the respiratory membrane (von Jagow et al. 1986). The known respiratory systems that lack quinones are aerobic. In these systems, the proton pumping cytochrome oxidase (Chan and Li 1990) is thought to be responsible for generating the Δ$\tilde{\mu}$ _H. The systems of anaerobic respiration involve a quinone (Kröger 1977; Wissenbach et al. 1990) with the exception of sulfur respiration (Paulsen et al. 1986; Schröder et al. 1988). Therefore, it is of interest to find out how the Δ$\tilde{\mu}$ _H is generated in this case. Here, we report on the most elaborate system of electron-transport-coupled phosphorylation with sulfur as acceptor, that is, the sulfur respiration of Wolinella succinogenes.