The Ground, or Resting, State

The ground state of bacteriorhodopsin, also called the initial, light-adapted, BR, or resting state, refers to the protein with a relatively 

Asp-96, a key residue in the middle of the relatively hydrophobic cytoplasmic half-channel about 11 A from the protonated Schilf base, is protonated in the ground state. Its only polar interaction stems from a hydrogen bond to the hydroxyl of Thr-46. Otherwise it is surrounded by a hydrophobic barrel whose walls are formed by residues IleA5, Leu-223, and Leu-224, and the lids by Phe-42, Leu-99, and Leu-100 on the cytoplasmic side, and by Val-49, Leu-93, and Phe-219 Schiff base side. In the M to N transition of the photocycle, reprotonation of the Schiffbase from Asp-96 can occur only after this hydrophobic region between the Schiffbase and Asp-96 has been populated by a chain of water molecules (Luecke et al., 2000b). 

Recent improvements in the details of the CLP crystallization procedure and crystal treatment have led to even better diffracting crystals. At 1.4 A resolution, refinement, including anisotropic B factors, illustrates, the thermal motion anisotropy of the retinal and key neighbors (Fig. 4, see color insert manuscript in preparation). 

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