Structural results from intermediate trapping studies of bacteriorhodopsin. Four structures of resting (Belrhali et al.
) (purple, Protein Data Bank entry 1qhj
), early (Edman et al.
) (blue, 1qkp
), intermediate (Royant et al.
) (green, 1eop
) and late (Luecke et al.
) (yellow, 1c8s
) conformations are shown. These intermediate conformations were trapped by illuminating crystals at 110 K, 170 K and during thawing, respectively. A clear evolution of the retinal can be observed for these structures, which moves towards the cytoplasm as the temperature is raised. Moreover, significant displacements of Trp-182, Asp-85 and Arg-82 are also observed, as are rearrangements of water molecules recorded in the corresponding Protein Data Bank entries (not shown for reasons of clarity).
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