Color Change of Proteorhodopsin by a Single Amino Acid Replacement at a Distant Cytoplasmic Loop

摘要

Visual and archaeal-type rhodopsins contain either 11-cis- or all-trans-retinal,respectively,inside the seven transmembrane helices.The retinal chromophore is bound to a lysine residue of the seventh helix through a protonated Schiff base linkage.The color-tuning mechanism is one of the important topics in the rhodopsin field because the color of a common molecule,either the 11-cis- or all-frans-retinal Schiff base,is determined by the surrounding amino acids of the protein.While we do not fully understand the mechanism,it is likely that color tuning is determined by various interactions between the retinal chromophore and the protein,such as electrostatic effects of charged groups,dipolar amino acids,and aromatic amino acids,hydrogen-bonding interactions,and steric contact effects.