THE TERMINAL QUINOL OXIDASES OF BACILLUS-SUBTILIS HAVE DIFFERENT ENERGY-CONSERVATION PROPERTIES

We have analyzed the respiratory chains in the logarithmic and station ary growth phases of Bacillus subtilis cells grown in rich glucose med ium. The cytochrome c branch of the respiratory chain was absent from both types of cells, which used a quinol oxidase branch for respiratio n. Cytochrome aa3-600 was found to be the major terminal oxidase in lo g phase cells. This enzyme was shown to translocate protons across the membrane in addition to the charge separation in the oxidation of qui nol. Both cytochromes d and aa3-600 were expressed in the stationary p hase. After inhibition of the latter by cyanide, cytochrome d was show n to catalyze charge separation during quinol oxidation, but not to pu mp protons across the membrane. A CO-binding membrane-bound cytochrome of approximately 17 kDa, called cytochrome b558, was presented in log phase cells. This protein did not exhibit oxidase activity and did no t have the characteristics of members of the conserved terminal oxidas e family.