Pore architecture of TRIC channels and insights into their gating mechanism

Ca2+ signalling is central to many fundamental activities of cells. Release of Ca2+ from intracellular stores is facilitated by sarcoplasmic or endoplasmic reticulum receptors including the A and B isoforms of the trimeric intracellular cation (TRIC) channel. These authors report the X-ray crystal structures of TRIC-B subtype channels from the roundworm Caenorhabditis elegans in the absence and presence of Ca2+. The structures reveal that the membrane protein forms a symmetrical homotrimeric complex, with an hourglass-shaped hydrophilic pore running through each monomer. The negatively charged head group of an endogenous lipid molecule interacts with the voltage-sensing helix, while its hydrophobic tails contribute to trimerization of TRIC channels.