Rhodopsin-carotenoid complexes in marine microorganisms
Microbial rhodopsins are retinal-bound, light-activated membranal proteins found in diverse aquatic microbes. In the ocean’s photic zone, >50% of microbes harbor a rhodopsin gene, potentially enabling their phototropic lifestyle. Recently, our lab reported on the widespread binding of carotene antennas to microbial rhodopsins, suggesting a significant impact on rhodopsin-mediated phototrophy.
Thus far, we have characterized novel antennas-rhodopsin complexes only from a bacterial origin. In this project, we screen for novel antennas-rhodopsin complexes from diverse microbial origins. Surprisingly, we found antennas-rhodopsin complexes originating from marine planktonic Asgard Archaea. Furthermore, we demonstrate that this rhodopsin can bind diverse hydroxylated carotenoids (e.g., lutein, diatoxanthin and fucoxanthin) and transfer energy. Our results indicate that the use of light-harvesting antennas in microbial rhodopsins is potentially utilized by open ocean Asgard Archaea to support phototrophic lifestyle
