Functional Interactions in Bacteriorhodopsin: a Theoretical Analysis of Retinal Hydrogen Bonding with Water
Overview
Affiliations
The light-driven proton pump, bacteriorhodopsin (bR) contains a retinal molecule with a Schiff base moiety that can participate in hydrogen-bonding interactions in an internal, water-containing channel. Here we combine quantum chemistry and molecular mechanics techniques to determine the geometries and energetics of retinal Schiff base-water interactions. Ab initio molecular orbital calculations are used to determine potential surfaces for water-Schiff base hydrogen-bonding and to characterize the energetics of rotation of the C-C single bond distal and adjacent to the Schiff base NH group. The ab initio results are combined with semiempirical quantum chemistry calculations to produce a data set used for the parameterization of a molecular mechanics energy function for retinal. Using the molecular mechanics force field the hydrated retinal and associated bR protein environment are energy-minimized and the resulting geometries examined. Two distinct sites are found in which water molecules can have hydrogen-bonding interactions with the Schiff base: one near the NH group of the Schiff base in a polar region directed towards the extracellular side, and the other near a retinal CH group in a relatively nonpolar region, directed towards the cytoplasmic side.
Structural insights into light-gating of potassium-selective channelrhodopsin.
Morizumi T, Kim K, Li H, Nag P, Dogon T, Sineshchekov O Nat Commun. 2025; 16(1):1283.
PMID: 39900567 PMC: 11790859. DOI: 10.1038/s41467-025-56491-9.
Structural Foundations of Potassium Selectivity in Channelrhodopsins.
Govorunova E, Sineshchekov O, Brown L, Bondar A, Spudich J mBio. 2022; 13(6):e0303922.
PMID: 36413022 PMC: 9765531. DOI: 10.1128/mbio.03039-22.
Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin.
Han C, Nguyen K, Berkow M, Hussain S, Kiani A, Kinnebrew M Biophys J. 2022; 122(1):168-179.
PMID: 36352784 PMC: 9822798. DOI: 10.1016/j.bpj.2022.11.012.
Channelrhodopsin C1C2: Photocycle kinetics and interactions near the central gate.
VanGordon M, Prignano L, Dempski R, Rick S, Rempe S Biophys J. 2021; 120(9):1835-1845.
PMID: 33705762 PMC: 8204341. DOI: 10.1016/j.bpj.2021.03.002.
Quantum Mechanical and Molecular Mechanics Modeling of Membrane-Embedded Rhodopsins.
Ryazantsev M, Nikolaev D, Struts A, Brown M J Membr Biol. 2019; 252(4-5):425-449.
PMID: 31570961 DOI: 10.1007/s00232-019-00095-0.