[Energy characteristics of the stages of photo-dependent transport of 14C-alanine in Halobacterium halobium R1 cells]

Abstract

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.