Two P Domain Potassium Channel Assays
Two P domain potassium channels (K2P) form leak channels which possess Goldman-Hodgkin-Katz rectification. Signaling lipids, oxygen tension, pH, mechanical stretch, and G-proteins are all involved in the regulation of these channels. They form dimers in the membrane and structurally correspond to two inward-rectifier subunits.
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Structure
K2P channel subunits have four different transmembrane helices (TM1–4) and two genuine pore sequences (P), which are positioned in the following order: TM1-P-TM2-TM3-P-TM4. K2P subunits so resemble a pair of Kir channel subunits assembled in tandem. Each subunit has a single pore sequence, which coalesce in the holo-channel to form a 4-fold, symmetric selectivity filter in the channel's center, which allows dehydrated K+ ions to pass through.
Feature
K2P potassium channel subunits are a new type of potassium channel subunit. They are active as dimers and have four transmembrane segments. These channels have a wide tissue distribution and can be found in both excitable and nonexcitable cells. Currents produced by K2P channels have peculiar features. They are noninactivating and quasi-instantaneous, active at all membrane potentials, and unaffected by traditional potassium channel blockers. In many cell types, they are predicted to play a key role in determining the resting membrane potential. Another distinguishing aspect of K2P channels is the wide range of regulation mechanisms available to them.
Published Data
| Paper Title | Mutation of a single residue promotes gating of vertebrate and invertebrate two-pore domain potassium channels |
| Journal | Nature Communications |
| Published | 2019 |
| Abstract | Understanding the biophysical factors that govern the gating of ion channels requires the use of mutations that alter their activity. Here, they demonstrate the conserved function of a single amino acid position (TM2.6) found in the second transmembrane domain of potassium (K2P) channels with two pore domains. All vertebrate K2P channels experience an increase in channel activity in response to TM2.6 mutations to aspartate or asparagine. |
| Result |
They created point mutations of TM2.6 to asparagine or aspartate in 16 distinct rodent and human K2P channels to see if the alteration could consistently improve the activity of vertebrate K2Ps. The total current generated by wild-type and mutant channels was then compared using two-electrode voltage-clamp recording in Xenopus oocytes. They discovered that in every instance, currents for TM2.6 mutants were noticeably augmented, and their preference for potassium was preserved as shown by noticeably hyperpolarized reversal potentials.
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Fig.1. Mutation of a single residue in TM2 systematically increases K2P channel activity. (Ben Soussia, 2019)
Reference
- Ben Soussia, I.; et al. Mutation of a single residue promotes gating of vertebrate and invertebrate two-pore domain potassium channels. Nature communications. 2019, 10(1): 787.
