CHARGE MOTIONS STUDIED IN THE BACTERIORHODOPSIN MUTANTS D85N AND D212N

The photoelectric response signals of the D85N and D212N bacteriorhodo psin mutants expressed in a Halobacterium halobium strain were measure d. The purple membranes containing only the mutant protein were orient ed and immobilized in polyacrylamide gel. The absorption changes and e lectric response signals were measured after laser excitation, enablin g the related charge motions in the protein to be followed during the photocycle. The signals were analysed on the basis of the sequential m odel with reversible reactions for the photocycle of the mutants. The transition lifetimes and electrogenicity of the intermediates were det ermined. From this analysis the relative electrogenicity of the L inte rmediate was established. The results corroborate the existence of a c onformational change during the photocycle in these bacteriorhodopsin mutants.