[Has the respiratory chain of Micrococcus lysodeiktocus any redox components on the outer surface of cytomembrane?]

M. lysodeikticus protoplasts have catalyzed the reduction of 5.10(-4) M ferricianide by endogenous substrates if the respiratory chain is inhibited by cyanide or anaerobiosis. A disturbance of the protoplast permeability by osmotic shock or Triton X-100 treatment resulted in the decrease of the endogenous ferricianide reduction rate and in simultaneous stimulation of malate ferricianide reductase activity in dehydrogenase site of the inner membrane surface. Reactivation of endogenous ferricianide reduction by protoplasts and the loss of malate stimulating activity were observed in hyperosmotic medium. Unlike malate oxidation by osmotically shocked protoplasts, endogenous protoplast repiration was resistant to ferricianide 5.10(-4) M). The latter, being added to protoplasts, induced the oxidation of anaerobically reduced cytochromes b556+560, and it practically did not affect cytochromes c552 and a601. The data obtained suggest that at least one of the respiratory chain components is arranged on the outer side of the protoplast membrane. This component is probably located in the cytochrome region. The results obtained confirm the hypothesis on transmembrane organization of the respiratory chain in M. lysodeikticus.