TY - JOUR
T1 - Electron diffraction studies of light-induced conformational changes in the Leu-93 → Ala bacteriorhodopsin mutant
AU - Subramaniam, Sriram
AU - Faruqi, A. R.
AU - Oesterhelt, Dieter
AU - Henderson, Richard
PY - 1997/3/4
Y1 - 1997/3/4
N2 - We previously have presented evidence for prominent structural changes in helices F and G of bacteriorhodopsin during the photocycle. These changes were determined by carrying out electron diffraction analysis of illuminated two-dimensional crystals of wild-type bacteriorhodopsin or the Asp-96 → Gly mutant that were trapped at a stage in the photocycle after light-driven proton release, but preceding proton uptake from the aqueous medium. Here, we report structural analysis of the long-lived O intermediate observed in the photocycle of the Leu-93 → Ala mutant, which accumulates after the release and uptake of protons, but before the reisomerization of retinal to its initial all-trans state. Projection Fourier difference maps show that upon illumination of the Leu-93 → Ala mutant, significant structural changes occur in the vicinity of helices C, B, and G, and to a lesser extent near helix F. Our results suggest that (i) all four helices that line the proton channel (B, C, F, and G) participate in structural changes during the late stages of the photocycle, and (ii) completion of the photocycle involves significant conformational changes in addition to those that are associated with steps in proton transport.
AB - We previously have presented evidence for prominent structural changes in helices F and G of bacteriorhodopsin during the photocycle. These changes were determined by carrying out electron diffraction analysis of illuminated two-dimensional crystals of wild-type bacteriorhodopsin or the Asp-96 → Gly mutant that were trapped at a stage in the photocycle after light-driven proton release, but preceding proton uptake from the aqueous medium. Here, we report structural analysis of the long-lived O intermediate observed in the photocycle of the Leu-93 → Ala mutant, which accumulates after the release and uptake of protons, but before the reisomerization of retinal to its initial all-trans state. Projection Fourier difference maps show that upon illumination of the Leu-93 → Ala mutant, significant structural changes occur in the vicinity of helices C, B, and G, and to a lesser extent near helix F. Our results suggest that (i) all four helices that line the proton channel (B, C, F, and G) participate in structural changes during the late stages of the photocycle, and (ii) completion of the photocycle involves significant conformational changes in addition to those that are associated with steps in proton transport.
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U2 - 10.1073/pnas.94.5.1767
DO - 10.1073/pnas.94.5.1767
M3 - Article
C2 - 9050853
AN - SCOPUS:0031042723
SN - 0027-8424
VL - 94
SP - 1767
EP - 1772
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 5
ER -