Charge transport in bacteriorhodopsin monolayers: The contribution of conformational change to current-voltage characteristics

TL;DR

This study models charge transport in bacteriorhodopsin monolayers, linking conformational changes to conductance variations, and extends the analysis to bovine rhodopsin, revealing contrasting light-induced conductance behaviors.

Contribution

It introduces a resistor network model based on protein structure to explain charge transport and validates it against experimental data, also applying it to another light-sensitive GPCR.

Findings

Light activation increases conductance in bacteriorhodopsin.

The model accurately reproduces experimental current-voltage characteristics.

Bovine rhodopsin shows decreased conductance upon light exposure.

Abstract

When moving from native to light activated bacteriorhodopsin, modification of charge transport consisting of an increase of conductance is correlated to the protein conformational change. A theoretical model based on a map of the protein tertiary structure into a resistor network is implemented to account for a sequential tunneling mechanism of charge transfer through neighbouring amino acids. The model is validated by comparison with current-voltage experiments. The predictability of the model is further tested on bovine rhodopsin, a G-protein coupled receptor (GPCR) also sensitive to light. In this case, results show an opposite behaviour with a decrease of conductance in the presence of light.