[W1-4] 光感受性膜タンパクである酵素ロドプシンの分子メカニズム
Function of microbial-type rhodopsins involve ion pump, ion channel, light sensor for phototaxis response. As these molecules are genetically targeted into various types of cells, they are widely applied as optogenetics tools for optical control of biological functions. Especially channelrhodopsins (ChR) and pump-type rhodopsins allow neuromodulation by depolarization or hyperpolarization of the membrane potentials. Since 2012, a new rhodopsin family, enzyme rhodopsin, has been discovered from microorganisms. Enzyme rhodopsins exhibit light activated enzymatic functions such as guanylate cyclase (Rh-GC) and phosphodiesterase (Rh-PD). More recently, a new type of enzymerhodopsin with near-infrared absorbing Rh-GC (NeoR) has been identified. These molecules could be genetically targeted into various types of cells, serving as optogenetics tools for optical control of intercellular cyclic nucleotide-associated signal transductions. To get deeper insights into the light-activation mechanism of Rh-GC and Rh-PDE, we here investigate the structural and spectroscopic properties, enzymatic kinetics, and evaluate the light-dependent activity in mammalian cells. Mutation studies were performed to identify critical residues for enzymatic activation. These results help understand their molecular mechanisms and develop optogenetic variants.