Issue 36, 2024

The retinal chromophore environment in an inward light-driven proton pump studied by solid-state NMR and hydrogen-bond network analysis

Abstract

Inward proton pumping is a relatively new function for microbial rhodopsins, retinal-binding light-driven membrane proteins. So far, it has been demonstrated for two unrelated subgroups of microbial rhodopsins, xenorhodopsins and schizorhodopsins. A number of recent studies suggest unique retinal–protein interactions as being responsible for the reversed direction of proton transport in the latter group. Here, we use solid-state NMR to analyze the retinal chromophore environment and configuration in an inward proton-pumping Antarctic schizorhodopsin. Using fully 13C-labeled retinal, we have assigned chemical shifts for every carbon atom and, assisted by structure modelling and molecular dynamics simulations, made a comparison with well-studied outward proton pumps, identifying locations of the unique protein–chromophore interactions for this functional subclass of microbial rhodopsins. Both the NMR results and molecular dynamics simulations point to the distinctive polar environment in the proximal part of the retinal, which may result in a hydration pattern dramatically different from that of the outward proton pumps, causing the reversed proton transport.

Graphical abstract: The retinal chromophore environment in an inward light-driven proton pump studied by solid-state NMR and hydrogen-bond network analysis

Supplementary files

Article information

Article type
Paper
Submitted
01 Jul 2024
Accepted
22 Aug 2024
First published
23 Aug 2024

Phys. Chem. Chem. Phys., 2024,26, 24090-24108

The retinal chromophore environment in an inward light-driven proton pump studied by solid-state NMR and hydrogen-bond network analysis

M. Pinto, M. Saliminasab, A. Harris, M. Lazaratos, A. Bondar, V. Ladizhansky and L. S. Brown, Phys. Chem. Chem. Phys., 2024, 26, 24090 DOI: 10.1039/D4CP02611J

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