The effect of lipid environment in purple membrane on bacteriorhodopsin

The decay rate of the Bacteriorhodopsin (BR) photocycle intermediate M412 and proton, the proton pump efficiency (H+/M412), the ratios of M412 to other intermediates and the rotational correlation time (τc) in purple membrane (PM) fragments treated by the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) with different concentrations were studied. The results show that: (1) The largest effect of CHAPS on M412 decay rate and proton decay rate of BR, τc of PM and the ratios of M412 to other intermediates in BR photocycle is in the range of its critical micelle concentration (CMC). This indicates that changes of the ratios of M412 to other intermediates, τc, M412 decay and proton decay occur and are due to the variation of the lipid environment. (2) The dependency of proton yield on CHAPS concentrations is basically consistent with that of M412s%. This indicates the relation between proton pumping function and M412. These studies show the importance of maintaining a native environment.