Electron paramagnetic resonance study of structural changes in the O photointermediate of bacteriorhodopsin.

ABSTRACT: The structural changes of bacteriorhodopsin during its photochemical cycle, as revealed by crystal structures of trapped intermediates, have provided insights to the proton translocation mechanism. Because accumulation of the last photointermediate, O, appears to be hindered by lattice forces in the crystals, the only information about the structure of this state is from suggested analogies with the determined structures of the non-illuminated D85S mutant and wild-type bacteriorhodopsin at low pH. We used electron paramagnetic resonance spectroscopy of site-directed spin labels at the extracellular protein surface in membranes to test these models. Spin-spin dipolar interactions in the authentic O state compared to the non-illuminated state revealed that the distance between helices C and

SUBMITTER: Chen D 

PROVIDER: S-EPMC1850110 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature