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"Manipulating Nature's Molecular Machines"

Dirk Trauner
(Universidade da Califórnia, Berkeley, USA)


The precise regulation of protein activity is fundamental to life. A mechanism of regulation, found across protein classes, from enzymes, to motors, to signaling proteins, is the allosteric control of an active site by a remote regulatory binding site. We describe a general approach for manipulating allosteric control with synthetic optical switches. Our strategy is exemplified with a ligand-gated ion channel of central importance in neuroscience, the ionotropic glutamate receptor (iGluR). Using structure-based design, we have modified its ubiquitous clamshell-type ligand-binding domain to develop a light-activated channel, which we call LiGluR. An agonist is covalently tethered to the protein through an azobenzene moiety, which functions as the optical switch. The agonist is reversibly presented to the binding site upon photoisomerization, initiating clamshell domain closure and concomitant channel gating.
     Light-activated ion channels such as LiGluR provide a precise and non-invasive optical means of controlling action potential firing in neurons, but the genes encoding these channels must first be delivered and expressed in target cells. To overcome this limitation, we have also developed a method for bestowing light-sensitivity onto endogenous ion channels that does not rely on exogenous gene expression.  The method utilizes the Photoswitchable Affinity Label (PAL), a synthetic light-switchable gate that is covalently tethered to native K+ channels. Both LiGluR and PAL have already found important applications in neurobiology.