Coupling Sites of the Respiratory Chain of Brevibacterium lactofermentum

Abstract

The respiratory chain system and respiration-linked proton translocation sites (coupling sites) of Brevibacterium lactofermentum were studied. The H⁺/0 ratio of the bacterium oxidizing endogenous substrates was approximately 4 g ions proton translocated per g atom oxygen consumed. The measurement of absorption spectra showed that the bacterium contained A-, B-, and C-type cytochromes. The H⁺/O ratios of cells loaded with specific substrates suggested that protons were translocated at the site 1 (NADH–Q) and the site 2 (Q–Cyt. c). Cytochrome oxidase (site 3) of the bacterium seems not to pump protons, although this bacterium has an oxidase of the cytochrome aa₃-type.