PROTON TRANSPORT AND M-TYPE INTERMEDIATE FORMATION BY 13-CIS-BACTERIORHODOPSIN

pH-titration of the dark-adapted 13-cis-retinal-containing bacteriorhodopsin (13-cis-bR) photocycle was performed in native and regenerated purple membranes, Triton X-100 solubilized and liposomal monomeric preparations. Under alkaline pH conditions the 13-cis-pigment component of these bR preparations was shown to enter into photochemical conversions, including the M-type intermediate, and was coupled to the transmembrane proton transfer. We observed that in the case of the monomeric detergent-treated bR the process of M formation in the 13-cis-bR photocycle is accompanied by a release of protons, subsequently uptaken simultaneously with the decay of the longwave O-like intermediate. In the 'collodion film-liposomal bR' system an electric response directly indicated a proton translocating activity in the 13-cis-bR at high pH. © 1990.