The pH-sensitive fluorescent protein Venus can be used as an optical reporter for proton flux when fused to an intracellular domain of Hv1 channels.

Slow inactivation has been described in multiple voltage-gated K+ channels and in great detail in the Drosophila Shaker channel. Structural studies have begun to facilitate a better understanding of the atomic details of this and other gating mechanisms. To date, the only voltage-gated potassium channels whose structure has been solved are KvAP (x-ray diffraction), the KV1.2-KV2.1 “paddle” chimera (x-ray diffraction and cryo-EM), KV1.2 (x-ray diffraction), and ether-à-go-go (cryo-EM); however, the structural details and mechanisms of slow inactivation in these channels are unknown or poorly characterized. Here, we present a detailed study of slow inactivation in the rat KV1.2 channel and show that it has some properties consistent with the C-type inactivation described in Shaker. We also study the effects of some mutations that are known to modulate C-type inactivation in Shaker and show that qualitative and quantitative differences exist in their functional effects, possibly underscoring subtle but important structural differences between the C-inactivated states in Shaker and KV1.2.

Voltage-dependent proton-permeable channels are membrane proteins mediating a number of important physiological functions. Here we report the presence of a gene encoding Hv1 voltage-dependent, proton-permeable channels in two species of reef-building corals. We performed a characterization of their biophysical properties and found that these channels are fast-activating and modulated by the pH gradient in a distinct manner. The biophysical properties of these novel channels make them interesting model systems. We have also developed an allosteric gating model that provides mechanistic insight into the modulation of voltage-dependence by protons. This work also represents the first functional characterization of any ion channel in scleractinian corals. We discuss the implications of the presence of these channels in the membranes of coral cells in the calcification and pH-regulation processes and possible consequences of ocean acidification related to the function of these channels.

AbstractC-type inactivation has been described in multiple voltage-gated K+ channels and in great detail in the Drosophila Shaker channel. As channels have moved into the structural era, atomic details of this and other gating mechanisms have started to be better understood. To date, the only voltage-gated channels whose structure has been solved are KvAP (X-ray diffraction), the KV1.2- KV2.1 “paddle” chimera (X-ray diffraction), KV1.2 (Cryo-EM); and ether-á-go-go (Cryo-EM) (Wang and MacKinnon, 2017), however, the characteristics and mechanisms of slow inactivation in these channels are unknown or poorly characterized. Here we present a detailed study of slow inactivation in the rat KV1.2 and show that it has some properties consistent with the C-type inactivation described in Shaker. We also study the effects of some mutations that are known to modulate C-type inactivation in Shaker and show that qualitative and quantitative differences exist in their functional effects, possibly underscoring subtle but important structural differences between the C-inactivated states in Shaker and KV1.2.

A native calcium ion channel has been identified in bacteria for the first time.