Mapping the molecular motions of 5-HT serotonin-gated channel by voltage-clamp fluorometry.

The serotonin-gated ion channel (5-HTR) mediates excitatory neuronal communication in the gut and the brain. It is the target for setrons, a class of competitive antagonists widely used as antiemetics, and is involved in several neurological diseases. Cryo-electron microscopy (cryo-EM) of the 5-HTR in complex with serotonin or setrons revealed that the protein has access to a wide conformational landscape.

Short-chain mono-carboxylates as negative modulators of allosteric transitions in Gloeobacter violaceus ligand-gated ion channel, and impact of a pre-β5 strand (Loop Ω) double mutation on crotonate, not butyrate effect.

Using the bacterial proton-activated pentameric receptor-channel Gloeobacter violaceus ligand-gated ion channel (GLIC): (1) We characterize saturated, mono-carboxylates as negative modulators of GLIC (as previously shown for crotonate; Alqazzaz et al., Biochemistry, 2016, 55, 5947). Butyrate and crotonate have indistinguishable properties regarding negative modulation of wt GLIC.

Mutational analysis to explore long-range allosteric couplings involved in a pentameric channel receptor pre-activation and activation.

Pentameric ligand-gated ion channels (pLGICs) mediate chemical signaling through a succession of allosteric transitions that are yet not completely understood as intermediate states remain poorly characterized by structural approaches. In a previous study on the prototypic bacterial proton-gated channel GLIC, we generated several fluorescent sensors of the protein conformation that report a fast transition to a pre-active state, which precedes the slower process of activation with pore opening. Here, we explored the phenotype of a series of allosteric mutations, using simultaneous steady-state fluorescence and electrophysiological measurements over a broad pH range.