Structure-function studies on bacteriorhodopsin. X. Individual substitutions of arginine residues by glutamine affect chromophore formation, photocycle, and proton translocation.
We have individually replaced all 7 of the arginine residues in bacteriorhodopsin by glutamine. The mutants with substitutions at positions 7, 164, 175, and 225 showed essentially the wild-type phenotype in regard to chromophore regeneration, chromophore lambda max, and proton pumping, although the mutant Arg-175----Gln showed decreased rate of chromophore regeneration. Glutamine substitutions of Arg-82, -134, and -227 affected proton pumping ability, and caused specific alterations in the bacteriorhodopsin photocycle. Finally, electrostatic interactions are proposed between Arg-82 and -227, and specific carboxylic acid residues in helices C and G, which regulate the purple to blue transition and proton transfers during the photocycle.
Stern
L J
LJ
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Khorana
H G
HG
D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001436:Bacteriorhodopsins / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001483:Base Sequence; D005973:Glutamine / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010788:Photosynthesis; D011522:Protons; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship
D011522:Protons; D005973:Glutamine; D001436:Bacteriorhodopsins; D001120:Arginine