ION PERMEABILITY INDUCED IN ARTIFICIAL MEMBRANES BY THE ATP ADP ANTIPORTER/

The hypothesis on the additional function of the ATP/ADP antiporter (A NT) as uncoupling protein has been tested in proteoliposomes and plana r bilayer phospholipid membranes (BLM). It is found that dissipation o f the light-induced Delta pH in the dark is very much faster in ANT-ba cteriorhodopsin proteoliposomes than in proteoliposomes containing bac teriorhodopsin as the only protein. Mersalyl treatment of ANT-bacterio rhodopsin proteoliposomes causes further increase in the Delta pH diss ipation rate due to formation of a high conductance pore. The properti es of this pore are studied on ANT incorporated to BLM. They proved to be similar to those of so-called multiple conductance channel or perm eability transition pore of inner mitochondrial membrane. The conducta nce of the single channel is as high as 2.2 nS. The channel fails to d iscriminate between K+, Na+, H+ and Cl-. Thus the obtained data are co nsistent with the assumption that native and modified ANT might functi on as an H+-specific conductor and as a permeability transition pore, respectively.