Download MendeleyRhodopsin from Haloquadratum walsbyi is a light-driven magnesium transporter.
Ko, L.N., Lim, G.Z., Chen, J.C., Ko, T., Li, G.Y., Yang, C.S.(2025) Nat Commun 16: 4472-4472
- PubMed: 40368960
- DOI: https://doi.org/10.1038/s41467-025-59795-y
- Primary Citation of Related Structures:
8XHW, 9JWS - PubMed Abstract:
The functionally unknown Middle rhodopsin (HwMR) is a microbial rhodopsin (mRho) identified in Haloquadratum walsbyi, an archaeon that thrives in a 2 M MgCl 2 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 Mg 2+ . Here, we show that HwMR can sense environmental Mg 2+ concentration via the D84 residue according to characteristic maximum absorption wavelength shift, photocycle kinetics, and Mg 2+ titration assay. X-ray crystallography of the wild-type HwMR and its D84N mutant produced two HwMR atomic structure models. Omit maps analysis of the wild-type HwMR model revealed D84 as a Mg 2+ binding site. On the cytoplasmic side, omit maps also revealed Mg 2+ association with T216. Both Mg 2+ sites were absent in the D84N mutant. A cell-based light-driven conductivity assay provided evidence to propose that HwMR is an inward magnesium transporter, with D84 as the primary binding site and T216 as the transportation stabilizing site. A sequential model was proposed to illustrate Mg 2+ transportation in HwMR.
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan, ROC.
Organizational Affiliation:
