Alomone Labs is pleased to offer the pH-Sensitive Kir Channel Antibody Explorer Kit (#AK-460). The Explorer Kit contains pH-sensitive Kir channel antibodies, ideal for screening purposes.
Kir channels are comprised of two transmembrane segments and form tetramers where the P-domain and TM2 contribute to the permeation pore structure. The elementary conductance of all Kir channels is dependent on extracellular K+ concentration over a large range. The subtypes Kir1.1, Kir4.X, Kir5.1 and Kir7.1 are involved in cell homeostasis and are sensitive to pH changes. Kir1.1, Kir4.1, and Kir4.2 are inhibited by intracellular acidification with pKa values of 6.5, 6.0, and 7.1, respectively. The association of Kir4.1 or Kir4.2 with Kir5.1 modifies the pKa of the heterotetramers, making these channels highly sensitive to pHi (Kir4.1-Kir5.1: 7.5; Kir4.2/Kir5.1: 7.6). At pH 7.3, a physiological pH, the open probability of Kir1.1, Kir4.1, and Kir4.2 is nearly maximal. These homotetramers are sensitive to intracellular acidification than to alkalization. The open probability of the heterotetramers Kir4.1/Kir5.1 and Kir4.2/Kir5.1 is largely lower, around 0.3–0.4, implying high sensitivity to pH changes in both directions. Kir7.1 exhibits a bell-shaped dependence on pH and appears rather insensitive to pH changes around pH 7.3.
Kir1.1 (also known as ROMK) was extensively researched but currently the pH sensing mechanism of this channel remains unclear. Previous studies have shown that Kir1.1 channels are closed by intracellular acidification with a pK1/2 of 6.5, and the mechanism for this regulation is a trio of basic residues R41, K80, and R311. The K80 lysine residue was identified as the sensor itself but this hypothesis is being challenged by the idea that pH modulation takes place by an effect on an intrinsic gating mechanism common to all Kir channels with pH sensitivity obeying the titration of a number of intracellular domain salt-bridges, stabilizing the channel in the open state1.
- Sepulveda, F.V. et al. (2015) Physiol. Rev. 95, 179.