Receptors have been identified for bitterness, sweetness and umami tastes, but not definitively for saltiness and sourness. Bill Schafer, Sun Wook Hwang and their teams find that the membrane protein TMC-1 is required for salt-aversion behaviour in the roundworm Caenorhabditis elegans, and show that it acts as an ion channel directly activated by sodium chloride in vitro. The human homologue of TMC-1 is associated with deafness, and this work makes it an attractive candidate for the long-sought cochlear hair-cell mechanotransduction channel. Mammals contain several TMC proteins of unknown function, and it is possible that one or more of these may have a role in sensory transduction processes such as touch or salt taste.
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