Structure changes upon deprotonation of the proton release group in the bacteriorhodopsin photocycle.

ABSTRACT: In the photocycle of bacteriorhodopsin at pH 7, a proton is ejected to the extracellular medium during the protonation of Asp-85 upon formation of the M intermediate. The group that releases the ejected proton does not become reprotonated until the prephotolysis state is restored from the N and O intermediates. In contrast, at acidic pH, this proton release group remains protonated to the end of the cycle. Time-resolved Fourier transform infrared measurements obtained at pH 5 and 7 were fitted to obtain spectra of kinetic intermediates, from which the spectra of M and N/O versus unphotolyzed state were calculated. Vibrational features that appear in both M and N/O spectra at pH 7, but not at pH 5, are attributable to deprotonation from the proton release group and resulting structural alte

SUBMITTER: Morgan JE 

PROVIDER: S-EPMC3414889 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature