Microbial rhodopsins are light-driven ion pumps found across diverse microorganisms, and they have become indispensable tools in optogenetics, where light is used to control the activity of cells. A research team has now characterized PoXeR, a novel rhodopsin identified from deep-sea microbial communities, revealing structural and functional features that distinguish it from previously known rhodopsins and expand the toolkit available for engineering light-controllable proteins.
Using a combination of structural and functional analyses, the researchers determined how PoXeR captures light energy and uses it to transport ions across cell membranes. The protein’s structure revealed a distinctive ion-conduction pathway and a set of residues that fine-tune its light absorption and pumping efficiency, setting it apart from rhodopsins found in surface-dwelling organisms.
The deep-sea origin of PoXeR is notable because organisms living at extreme ocean depths face unique environmental pressures, including minimal light availability and high pressure, that can shape the evolution of light-sensing and light-harvesting proteins in unexpected ways. The researchers suggest that these evolutionary pressures may have produced a rhodopsin with properties well suited to biotechnological applications.
By clarifying the structural basis of PoXeR’s ion-pumping mechanism, the study provides a foundation for engineering the protein for use in optogenetic research, where precisely controlled light-activated proteins are used to manipulate the activity of neurons and other cells. The findings also expand scientific understanding of the diversity of microbial rhodopsins found in the world’s oceans, particularly in the relatively unexplored deep sea.
The researchers say further work will be needed to fully characterize PoXeR’s behavior in engineered systems and to explore whether related rhodopsins from other deep-sea microbes hold similarly useful properties.
Journal: Cell Research