[Photogeneration of a 2-vector transmembrane proton gradient in Halobacterium halobium R1 cells]

Abstract

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.