[Generation of membrane potential by aerobic bacteria Micrococcus lysodeikticus. Correlation between coupled and uncoupled respiration]. / Generatsiia membrannogo potentsiala aérobnymi bakteriiami Micrococcus lysodeikticus. Sootnoshenie sopriazhennogo i nesopriazhennogo dykhaniia.

The effects of cyanide and nonylhydroxyquinoline-N-oxide on membrane potential generation and oxidase activities in intact cells and membrane particles of M. lysodeikticus were studied. Low concentrations of the inhibitors interacting with the components of one branch of a branched respiratory chain of M. lysodeikticus strongly inhibit the membrane potential generation and only slightly reduce the total respiration rate. It was assumed that the generation of delta psi takes place in the b-c locus of the respiratory chain branch terminated with cytochrome oxidase; over 90% of total O2 uptake provides for the uncoupled respiration via cytochrome omicron. Inside the b-c locus two sites responsible for delta psi generation were singled out; these sites differ in their sensitivities towards nonylhydroxyquinoline-N-oxide. Based on the data obtained and the effect of "extra-reduction" of cytochrome b566 a hypothetical model of the respiratory chain of M. lysodeikticus was developed, which includes the branching of the electron flux to two terminal pathways and redox equivalent transport cyclization via the menaquinone cycle. The physiological role of uncoupled respiration through cytochrome omicron is discussed.

[Redox-dependent protonation of cytochrome oxidase hemes in submitochondrial particles of the bovine heart]. / Redoks-zavisimoe protonirovanie gemov tsitokhromoksidazy v submitokhondrial'nykh chastitsakh serdtsa byka.

Potentiometric titrations of cytochrome oxidase in bovine heart submitochondrial particles were carried out within the pH range 5.3-9.0 in the alpha-band of heme absorption. The data obtained were analyzed within a model of non-interacting hemes and in accordance with a "neoclassical" scheme implying heme--heme interactions between cytochromes a and a3. The individual pH-dependencies of half-reduction potentials of cytochromes a and a3 were determined. It was found that the redox-dependent protonation (the oxidation Bohr effect) is characteristic of the both cytochromes; however, the reduction of one of the hemes significantly diminishes the Bohr effect for the second heme. The redox transitions of cytochrome a are coupled to ionization of at least two heme-linked acid-base groups of the enzyme with pK1(red) in the acidic and pK2(ox) in the alkaline regions of pH, whereas the pH dependence of E0' for cytochrome a3 fits to the model containing one hemi-linked group with a pKred in the acidic region.

[Repair of membrane damage caused by low temperature freezing of E. coli cells]. / Izuchenie reparatsii povrezhdenii membrannogo apparata, vyzvannykh nizkotemperaturnym zamorazhivaniem kletok E. coli.

Low temperature freezing of E. coli cells causes an almost complete cell damage. A transfer of the frozen cells to nutritional media results in a repair of some of the damages, i.e. in reconstitution of the barrier stability of the E. coli outer membrane detected by a decrease in sensitivity of the frozen cells to the detergent and lysozyme action and in a change of the cell membrane potential measured by the penetrating ion method. The repair of the cytoplasmic membrane damage is followed by the changes in the permeability barrier for H+ and endogenous substrates, which results in restoration of ATP synthesis as a response to the artificial proton motive force and in an induction of beta-galactosidase synthesis. At the same time the synthesis of the periplasmic protein, alkaline phosphatase, in the cells after repair remains suppressed. An analysis of various biosynthetic processes demonstrated that the inhibition of lipid synthesis completely suppresses the reduction processes, while protein synthesis is not necessary for the repair. The importance of the transmembrane electrochemical proton gradient for the repair processed in E. coli cells was established; the ATP biosynthesis essential for the repair occurs, in all probability, via the glycolytic pathway and not via oxidative phosphorylation.