Schiff Base Proton Acceptor Assists Photoisomerization of Retinal Chromophores in Bacteriorhodopsin
نویسندگان
چکیده
منابع مشابه
Aspartic acid 85 in bacteriorhodopsin functions both as proton acceptor and negative counterion to the Schiff base.
In bacteriorhodopsin Asp85 has been proposed to function both as a negative counterion to the Schiff base and as proton acceptor in the early stages of the photocycle. To test this proposal further, we have replaced Asp85 by His. The rationale for this replacement is that although His can function as a proton acceptor, it cannot provide a negative charge at residue 85 to serve as a counterion t...
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The membrane protein bacteriorhodopsin contains all-trans-retinal in a binding site lined by amino acid side groups and water molecules that guide the photodynamics of retinal. Upon absorption of light, retinal undergoes a subpicosecond all-trans-->13-cis phototransformation involving torsion around a double bond. The main reaction product triggers later events in the protein that induce pumpin...
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In order to understand how isomerization of the retinal drives unidirectional transmembrane ion transport in bacteriorhodopsin, we determined the atomic structures of the BR state and M photointermediate of the E204Q mutant, to 1.7 and 1.8 A resolution, respectively. Comparison of this M, in which proton release to the extracellular surface is blocked, with the previously determined M in the D9...
متن کاملConformational Effects on the Proton Affinity of the Schiff Base in Bacteriorhodopsin: A Density Functional Study
Density functional theory (DFT) calculations have been performed on a number of Schiff base structures related to the retinal Schiff base in bacteriorhodopsin (BR). The proton affinity (PA) of the Schiff base group was calculated in species with different lengths of the conjugated double-bond system and at different cis/trans isomerization states. The results show that the length of the conjuga...
متن کاملSchiff Base Switch II Precedes the Retinal Thermal Isomerization in the Photocycle of Bacteriorhodopsin
In bacteriorhodopsin, the order of molecular events that control the cytoplasmic or extracellular accessibility of the Schiff bases (SB) are not well understood. We use molecular dynamics simulations to study a process involved in the second accessibility switch of SB that occurs after its reprotonation in the N intermediate of the photocycle. We find that once protonated, the SB C15 = NZ bond ...
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ژورنال
عنوان ژورنال: Biophysical Journal
سال: 2017
ISSN: 0006-3495
DOI: 10.1016/j.bpj.2017.05.015