3.E.1.7.14
Cation channel rhodopsin, CCR4, of 398 aas and 7 TMSs has higher light sensitivity than typical channelrhodopsins, and it shows superior properties as an optogenetic tool, such as minimal desensitization (Tanaka et al. 2024). Structural analyses of GtCCR2 and GtCCR4 revealed that GtCCR4 has an outwardly bent transmembrane helix, resembling the conformation of activated G-protein-coupled receptors. Spectroscopic and electrophysiological comparisons suggested that this helix bend in GtCCR4 omits channel recovery time and contributes to high light sensitivity. An electrophysiological comparison of GtCCR4 and the well-characterized optogenetic tool ChRmine revealed that GtCCR4 has superior current continuity and action-potential spike generation with less invasiveness in neurons (Tanaka et al. 2024).