QUANTITATIVE MODEL FOR THE COOPERATIVE INTERACTION OF THE BACTERIORHODOPSIN MOLECULES IN PURPLE MEMBRANES

The trimeric, asymmetric and sequential model for the cooperative inte raction of the bacteriorhodopsin molecules in purple membranes [Zs, To kaji, Biophys. J. 65 (1993) 1130-1134] is being extended in the paper, Analyses of data from absorption kinetic measurements with preexcitat ion and green background illumination, and photoselection measurements on oriented samples confirm the main features of this cooperative int eraction and support the validity of the extended model, This model in cludes the observed heterogeneity of the non-excited state of the bact eriorhodopsin molecules in purple membranes, and the agreement with th e data suggests that molecules in any other state than the baeteriorho dopsin ground state can alter the photocycle of their neighbors, The p resented results seem to contradict other models for the cooperation o f the bacteriorhodopsin molecules. (C) 1998 Federation of European Bio chemical Societies.