The effect of lipid environment in purple membrane on bacteriorhodopsin

The decay rate of the Bacteriorhodopsin (BR) photocycle intermediate M-412 and proton, the proton pump efficiency (H+/M-412), the ratios of M-412 to o ther intermediates and the rotational correlation time (tau (c)) in purple membrane (PM) fragments treated by the zwitterionic detergent 3-[(3-cholami dopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) with different concen trations were studied. The results show that: (1) The largest effect of CHA PS on M-412 decay rate and proton decay rate of BR, tau (c) of PM and the r atios of M-412 to other intermediates in BR photocycle is in the range of i ts critical micelle concentration (CMC). This indicates that changes of the ratios of M-412 to other intermediates, tau (c), M-412 decay and proton de cay occur and are due to the variation of the lipid environment. (2) The de pendency of proton yield on CHAPS concentrations is basically consistent wi th that of M-412s%. This indicates the relation between proton pumping func tion and M-412. These studies show the importance of maintaining a native e nvironment. (C) 2000 Elsevier Science B.V. All rights reserved.