The evolutionary relationship of rhodopsin proteins across species

Rhodopsin is a binding protein consisting of retinal and seven transmembrane proteins which can absorb light and cause a series of light-induced reactions within any organism. This kind of protein is not only discovered in animals' eyes, but also found in a wide range of microbes in recent years. Microbial rhodopsin is further divided into different categories that carry out different functions, including proton pump, ion pump, and optical driver. Past research has hypothesized the existence of certa in connections between animal and microbial rhodopsin. Therefore, this research collects information about various kinds of microbial rhodopsin (BR, HR, SRI, SRII) as well as animal rhodopsin sequences and explores their evolutionary relationship through the phylogenetic tree and transmembrane domain analysis. The results show that both HR and SR evolved from BR. As for the evolutionary relationship between microbial and animal rhodopsin, this research agrees with the conclusion of preexisting research: though they share conservative structures, their evolutionary relationship is still not supported by solid evidence.