[Energy characteristics of the stages of photo-dependent transport of 14C-alanine in Halobacterium halobium R1 cells]. / Energeticheskaia kharakteristika stadii fotozavisimogo transporta 14C-alanina v kletki Halobacterium halobium R1.

The energy of light is utilized by Halobacterium halobium R1 only at the very beginning of illumination at the same time as the transport of protons into the cells, as follows from comparing the data of photophosphorylation and light-dependent transport. The release of protons by the cells on further illumination suggests that the photoprocess and the accumulation of energy by the cells are being uncoupled. The primary transport of 15C-alanine in the course of illumination is caused directly by electrochemical gradient (i) whereas the secondary transport in the dark involves the energy liberated on hydrolysis of ATP which has been formed in the process of photophosphorylation (II). An indirect technique of assaying ATP from the transport of 14C-alanine into the cells makes it possible to characterize the distribution of utilized light energy between photophosphorylation (II) and transport processes (I). The bulk of energy is accumulated as ATP. The incorporation of 14C-alanine into the cells is stimulated twofold by illumination for a long time under physiological conditions in the presence of respiration. Therefore, light plays an important role in the energy balance of H. halobium R1.

[Photogeneration of a 2-vector transmembrane proton gradient in Halobacterium halobium R1 cells]. / Fotogeneratsiia dvukhvektornogo transmembrannogo gradienta protonov v kletkakh Halobacterium halobium R1.

Analysing 4 phases of light-dependent change of pH in cell suspension of H. halobium R1 it has been found that an increase of pH I when light is switched on and a decrease of pH II during further illumination are proportional to the light effect and are energy-dependent. Neutralization of these changes (phases III and IV) proceeds spontaneously in the darkness. These data show that the transmembrane gradient of protons is generated in two directions--delta pH and +delta pH, simultaneous presence of which points to the local character of one of them. Generation of -delta pH associated with light energy utilization by the cells is considered as a result of neutralization of the negative charge and +delta pH1 (latent), appearing due to a change in bacteriorodopsin conformation under illumination. It may be also suggested that the yield of protons from the cells of pHII and generation of +delta pH result from the discoupling of photoprocesses and energy utilization by the cells, containing bacteriorodopsin.

Reconstitution of Biological Molecular generators of electric current. Bacteriorhodopsin.

1. Photoinduced generation of electric current by bacteriorhodopsin, incorporated into the planar phospholipid membrane, has been directly measured with conventional electrometer techniques. 2. Two methods for bacteriorhodopsin incorporation have been developed: (a) formation of planar membrane from a mixture of decane solution of phospholipids and of the fraction of violet fragments of the Halobacterium halobium membrane (bacteriorhodopsin sheets), and (b) adhesion of bacteriorhodopsin-containing reconstituted spherical membranes (proteoliposomes) to the planar membrane in the presence of Ca2+ or some other cations. In both cases, illumination was found to induce electric current generation directed across the planar membrane, an effect which was measured by macroelectrodes immersed into electrolyte solutions on both sides of the membrane. 3. The maximal values of the transmembrane electric potential were of about 150 mV at a current of about 10(-11) A. The electromotive force measured by means of counterbalancing the photoeffect by an external battery, was found to reach the value of 300 mV. 4. The action spectrum of the photoeffect coincides with the bacteriorhodopsin absorption spectrum (maximum about 570 nm). 5. Both components of the electrochemical potential of H+ ions (electric potential and delta pH) across the planar membrane affect the bacteriorhodopsin photoelectric response in a fashion which could be expected if bacteriorhodopsin were a light-dependent electrogenic proton pump. 6. La3+ ions were shown to inhibit operation of those bacteriorhodopsin which pump out H+ ions from the La3+-containing compartment. 7. The photoeffect, mediated by proteoliposomes associated with thick planar membrane, is decreased by gramicidin A at concentrations which do not influence the planar membrane resistance in the light. On the contrary, a protonophorous uncoupler, trichlorocarbonylcyanidephenylhydrazone, decreases the photoeffect only if it is added at a concentration lowering the light resistance. The dark resistance is shown to be higher than the light one, and decreases to the light level by gramicidin. 8. A simple equivalent electric scheme consistent with the above results has been proposed.

[Biphasic nature of the light-dependent transport of C14-alanine into Halobacterium holobium cells]. / Dvukhfaznyi kharakter fotozavisimogo transporta C14-alanina v kletki Halobacterium halobium

Biphase character of photoinduced pH change in H. halobium R1 suspension cells is shown: in the first illumination period pH rises and only afterwards it decreases. pH increase is accompanied by the introduction of C14-alanine into the cells, while the decrease by its yield up to the level lower than the "dark" one ("negative" photoeffect). The bi-phase character of transport processes seems to be explained by the reversible character of light-dependent bacteriorodopsin proton pump in H. halobium R1 cells.