Rhodopsin from Haloquadratum walsbyi is a light-driven magnesium transporter.

ABSTRACT: The functionally unknown Middle rhodopsin (HwMR) is a microbial rhodopsin (mRho) identified in Haloquadratum walsbyi, an archaeon that thrives in a 2 M MgCl₂ environment harmful to most other microorganisms. HwMR shares conserved and functionally critical residues with both bacteriorhodopsin (BR), a proton pump, and sensory rhodopsin II (SRII), which mediates phototaxis, even though HwMR exerts neither function. We previously reported HwMR as a unique mRho found to associate with Mg²⁺. Here, we show that HwMR can sense environmental Mg²⁺ concentration via the D84 residue according to characteristic maximum absorption wavelength shift, photocycle kinetics, and Mg²⁺ titration assay. X-ray crystallography of the wild-type HwMR and its D84N mutant pr

SUBMITTER: Ko LN 

PROVIDER: S-EPMC12078690 | biostudies-literature | 2025 May

REPOSITORIES: biostudies-literature