Microbial Rhodopsins: Diversity, Mechanisms, and Optogenetic Applications

• Published in: Annual review of biochemistry Vol. 86; no. 1; pp. 845 - 872
• Main Authors: Govorunova, Elena G, Sineshchekov, Oleg A, Li, Hai, Spudich, John L
• Format: Journal Article
• Language: English
• Published: United States Annual Reviews 20.06.2017; Annual Reviews, Inc
• Subjects: Algae; anion channelrhodopsins; Aquatic plants; Atmospheric chemistry; cation channelrhodopsins; Chemical reactions; Chlorophyta - classification; Chlorophyta - genetics; Chlorophyta - metabolism; Evolution, Molecular; Gene Expression; Genetics; Information processing; ion pumps; Light; Light Signal Transduction; Membrane potential; Membrane Potentials - physiology; Membranes; Microorganisms; Models, Molecular; Optics; optogenetics; Optogenetics - methods; Photochemical Processes; Photochemical reactions; Photochemicals; photosensors; Phylogeny; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Domains; Proteins; Retinoids - chemistry; Retinoids - metabolism; Retinylidene proteins; Rhodopsins, Microbial - chemistry; Rhodopsins, Microbial - genetics; Rhodopsins, Microbial - metabolism; Scaffolds; Sensory Rhodopsins - chemistry; Sensory Rhodopsins - genetics; Sensory Rhodopsins - metabolism; Sensory transduction; Signal transduction; Therapeutic applications; photosensors; cation channelrhodopsins; ion pumps; optogenetics; retinylidene proteins; anion channelrhodopsins
• ISSN: 0066-4154; 1545-4509
• DOI: 10.1146/annurev-biochem-101910-144233

Microbial rhodopsins are a family of photoactive retinylidene proteins widespread throughout the microbial world. They are notable for their diversity of function, using variations of a shared seven-transmembrane helix design and similar photochemical reactions to carry out distinctly different light-driven energy and sensory transduction processes. Their study has contributed to our understanding of how evolution modifies protein scaffolds to create new protein chemistry, and their use as tools to control membrane potential with light is fundamental to optogenetics for research and clinical applications. We review the currently known functions and present more in-depth assessment of three functionally and structurally distinct types discovered over the past two years: ( a ) anion channelrhodopsins (ACRs) from cryptophyte algae, which enable efficient optogenetic neural suppression; ( b ) cryptophyte cation channelrhodopsins (CCRs), structurally distinct from the green algae CCRs used extensively for neural activation and from cryptophyte ACRs; and ( c ) enzymerhodopsins, with light-gated guanylyl cyclase or kinase activity promising for optogenetic control of signal transduction.