Abstract The voltage-gated Hv1 proton channel is a member of voltage-gated ion channel family, it plays a key role in the acid extrusion from excitable and non-excitable cells and regulate pH homeostasis in a variety of cell types. The Hv1 proton channel provides charge and pH compensation during the respiratory burst of the phagocyte NADPH oxidase and controls production of reactive oxygen species in phagocytes, it mediates proton efflux at the pulmonary alveolar cell membrane and acidifies excessively alkaline airway surface liquid in the airway cells. Hv1 is found to be a sperm flagellar regulator of intracellular pH, and play a crucial role in sperm capacitation. In addition, Hv1 activity is required for acid extrusion to shape action potentials in snail neurons. Studies have shown that biophysical properties and functions of the Hv1 channel are not identical in a variety of tissues, the distinct manifestations of native voltage-gated proton channels in different cell types indicate the existence of modulatory partners modulating the Hv1 proton channel's function. We recently identified a family of transmembrane protein as the Hv1 channel interactor. We discovered that the presence of the transmembrane protein alters the Hv1 channel's activity and modulates the channel's voltage-dependent gating. The goal of this proposal is designed to determine the effects of the transmembrane protein on the Hv1 channel physiology, biophysics, and pharmacology. The proposed research will establish the physiological relevance of Hv1 channel regulation by transmembrane modulators and shed light on novel voltage-gated ion channel regulatory mechanisms.