Microbial rhodopsins, also known as bacterial rhodopsins are retinal-binding proteins that provide light-dependent ion transport and sensory functions in halophilic and other bacteria. They are integral membrane proteins with seven transmembrane helices, the last of which contains the attachment point (a conserved lysine) for retinal. Contrary to their name, microbial rhodopsins are found not only in Archaea and Bacteria, but also in Eukaryota (such as algae) and viruses; although they are rare in complex multicellular organisms.