CULTURE TEMPERATURE AFFECTS THE MOLECULAR-MOTION OF BACTERIORHODOPSINWITHIN THE PURPLE MEMBRANE

We measured the absorption anisotropies of bacteriorhodopsin (bR) with in a purple membrane suspension after photo-excitation in the millisec ond time range, The purple membranes used were isolated from Halobacte rium salinarium grown at three different culture temperatures, 37.0, 4 3.0 and 47.5 degrees C, For the membranes from the 37.0 degrees C cult ure, the observed anisotropies at wavelengths of 410, 570 and 680 nm s howed almost the same slow decay, The slow decaying of the anisotropie s originated from the rotation of the membrane itself, Using the membr anes from the 43.0 and 47.5 degrees C culture, however, we found that the anisotropy change varied at each wavelength measured, In these cas es, it is shown from detailed data analysis that 1) the rotational mot ion of photo-intermediates within the membrane is more restricted than that of non-excited bR and 2) the distorted arrangements of the prote ins within the membrane remain, even after photo-intermediates return to ground-state bR. This restricted motion is probably caused by the c onformational changes in photo-intermediates, which prevent the rotati on of the monomer protein and/or lead photo-intermediates to bind with neighboring proteins.