Effect of introducing different carboxylate-containing side chains at position 85 on chromophore formation and proton transport in bacteriorhodopsin.

摘要: Abstract During the initial stages of bacteriorhodopsin photocycle, a proton is transferred from Schiff base to deprotonated carboxylate Asp85. Earlier studies have shown that replacement Asp85 by Asn completely abolishes transport activity, whereas extension side chain an additional carbon-carbon bond (Asp85-->Glu) results in functional pump. Here we show two lengths also pump as long terminal group moiety. These chains were created modification cysteine residue Asp85-->Cys mutant with either iodoacetic acid or iodoacetamide. In vitro chromophore formation rate protonation mutants contain at 85 invariably faster than neutral substitutions this position. We conclude bacteriorhodopsin, there considerable tolerance volume can be accommodated position and presence important both for pumping stabilizing protonated base.