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Abstract

The scheme of the bacteriorhodopsin photocycle associated with a transmembrane proton transfer and electrogenesis is considered. The role of conformational changes in the polypeptide chain during the proton transport is discussed.

Bacteriorhodopsin. Correspondence of the photocycle and electrogenesis with sites of the molecule

“…The photopotential (∆V) at every stage of the process is directly proportional to the projection (r) of the pathway of the proton movement onto the normal to the mem brane and inversely proportional to the dielectric con stant (ε) of the membrane: ∆V ~ kr/ε. Different phases of this response with the photocycle intermediates and structure of the molecule have been compared in detail earlier [2,3], and this comparison is summarized in the figure with regard to new literature data [5,8,9] and our findings. The file with 1c3w coordinates [10] contains the best current X ray diffraction analysis data on the BR molecule and is widely used in modern studies on BR.…”

“…The potential difference in the resulting system were directly determined [2,7]. The electrogenesis was induced by a laser light flash, which caused a single turnover of the photocycle.…”

“…The hypotheses describing the functions of every proton transporting site should reasonably agree with the experimentally observed potential difference generated at the stage under study and the distance traveled by the charges per pendicularly to the PM surface. In our previous paper [2], attention was paid to this agreement, and the pur pose of the present work was to study this problem more in detail.…”

“…The photocycle transitions correspond to conformational changes in the molecule, which pro vide the charge transfer across the membrane. A single turnover of the photocycle results in transfer of not a sin gle proton but of a number of protons between certain groups, and this ensures the transfer of one H + across the whole thickness of the purple membrane (PM) [2]. Although the fundamental construction of the proton transport chain is more or less clear [2 5], functions of its separate sites need to be detailed.…”

“…PMs were associated with an artificial flat lecithin membrane reinforced with a collodion film [2,7].…”