[Dynamic organization of the electron transport chain in bacterial membrane by radiation inactivation]. / Issledovanie dinamicheskoi organizatsii élektrontransportnoi tsepi v bakterial'noi membrane metodom radiatsionnoi inaktivatsii.

A complete cross-linking of proteins in isolated Micrococcus lysodeikticus membranes under effect of glutaric aldehyde causes 50% inhibition of the NADH-oxidase activity. Using the irradiation inactivation procedure, it was demonstrated that the size of the irradiation target for NADH-oxidase coincides with that for NADH-dehydrogenase and makes up to about 50 KD. In glutaric aldehyde-treated membranes the target size for NADH-oxidase is 3 times more than that, i.e. 150 KD. It is assumed that the effective electron transfer is mediated by a carrier assembly united into a supramolecular complex with a terminal life-time. Different assemblies exchange their components due to lateral diffusion of proteins in the membrane, which can account for the small size of the irradiation target for the oxidase activity.

Respiratory chain of bacterial membrane: assembly-mobile carriers equilibrium.

The target size of NADH-oxidase activity of M. lysodeikticus isolated membranes for electron radiation is nearly equal to that obtained for NADH-dehydrogenase (about 50 kD). The complete cross-linking of membrane proteins by glutaraldehyde causes an increase of NADH-oxidase target size to 3-3.5 times its original value. Electrons are transported by cross-linked respiratory chain from NADH to O2 with 60-50% effectiveness of that in untreated membranes. It is proposed that electrons are transported through a multi-enzymic complex of individual carriers having limited lifetime with exchange of carriers between different respiratory complexes via lateral diffusion in membrane.

[Structure of the Micrococcus lysodeikticus respiratory chain using low concentrations of Triton X-100 and glutaric aldehyde]. / Issledovanie organizatsii dykhatel'noi tsepi Micrococcus lysodeikticus s pomoshch'iu malykh kontsentratsii tritona X-100 i glutarovogo al'degida.

Using low (0.0025 -- 0.025%) concentrations of Triton X-100, the correlation between the decrease of NADN- and malate oxidase activities and NADH- and malate dehydrogenase release in large fragments of Micrococcus lysodeikticus membranes was established. This was accompanied by membrane suspension clearance and a decrease of microviscosity of the membrane lipid component. Using NADH-dehydrogenase, it was shown that the attachment of NADH-dehydrogenase to the membrane treated with glutaric aldehyde occurs in two steps, this being indicative of different environment of this enzyme in the membrane. The data obtained are discussed in terms of laterally heterogenous structure of the bacterial membrane with respect to the electron transport enzymes, in particular in favour of an existence of individual sites of the membrane containing dehydrogenases rather than other respiratory chain components.

[Lateral heterogeneity of bacterial membranes]. / Lateral'naia neodnorodnost' bakterialnoi membrany.

Isolated membranes of M. lysodeikticus were rapidly frozen and disrupted in a Hughes press. After disruption the fragments were centrifuged at 144000 g for 1 hour and part of the supernatant just above the pellet was subjected to isopycnic centrifugation in a continuous sucrose density gradient. It was found that the material tested was a mixture of fragments differing in their buoyant densities. These fragments also differed in their protein/lipid ratios, cytochrome content and dehydrogenase activities calculated per protein and lipid as well as in proportion of the respiratory chain enzymes. The results obtained are indicative of lateral heterogeneity of the bacterial membrane and the existence of areas in the membrane having high concentration of the respiratory chain enzymes. The latter may suggest that the system of substrate oxidation is segregated in the membrane. It is assumed that there exists in the membrane an exchange of components between different electron-transporting chains operated due to their lateral diffusion.