The retinylidene Schiff base counterion in bacteriorhodopsin.

Abstract

The abbreviations used are: bR, bacteriorhodopsin; ebR, bacteriorhodopsin prepared by expression of a synthetic wild-type gene in E. coli; PSB, the protonated Schiff base; SB, the unprotonated Schiff base; DA, the dark-adapted form of the chromophore; LA, the lightadapted form of the chromophore; DMPC, L-a-dimyristoylphosphatidylcholine; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-l- propanesulfonate; SDS, sodium dodecyl sulfate.* bR mutants are designated by the wild-type amino acid residue (standard one-letter code) and its position number followed by the substituted amino acid residue.Thus, "R82Q signifies the mutant in which the arginine at position 82 has been replaced by glutamine, and "D85N/D212N" signifies the double mutant in which the two aspartates at positions 85 and 212 have been replaced by asparagines. 18674