[Some features of photochemical conversions of bacteriorhodopsin at low pH values]

Association of bacteriorhodopsin sheets and proteoliposomes with collodium film impregnated with a lecithine solution in decane was carried out. The generation of electrical potential difference in response to a light flash within the pH range of 0-6 was studied. The amplitude of microsecond (II) and millisecond (III) phases of the photoelectrical response was shown to decline with a decrease in pH as in the case when the inhibition by acid is due to protonation of a group with a pK of 3,7. The photoelectrical response of the "acid" form of bacteriorhodopsin with a maximun at 605 nm is represented by a negative phase having a small amplitude. This phase is coupled with the formation of the photochemical cycle bathointermediate and is sharply increased in an acid medium simultaneously with the generation of bacteriorhodopsin form with an absorption maximum at 565 nm. The effects of KCl, phenyldicarbaundecaborane and fluoride on the spectral and photoelectrical responses of bacteriorhodopsin are described.