Subtype-specific Gating Mechanisms of OTOP Channels by Protons

Otopetrin (OTOP) channels are proton-selective ion channels conserved among vertebrates and invertebrates and with no structural similarity to other ion channels. There are three vertebrate OTOP channels (OTOP1, OTOP2, and OTOP3, of with one (OTOP1) functions as a sour taste receptor. However, whether and by what the channels are gated was not known. To address this question, we compared the functional properties of the three murine OTOP channels heterologously expressed in HEK-293 cells to varying extracellular pH (pHo).