1.B.1.1.24
Porin 2 (Omp-Pst2 or OmpPst2) of 365 aas.  Voltage gating is observed for Omp-Pst2, where the binding of cations in-between L3 and the barrel wall results in exposing a conserved aromatic residue in the channel lumen, thereby halting ion permeation. Comparison of Omp-Pst1 (TC# 1.B.1.1.20) with Omp-Pst2 suggested that their differing sensitivities to voltage is encoded in the hydrogen-bonding network anchoring L3 onto the barrel wall. The strength of this network governs the probability of cations binding behind L3. That Omp-Pst2 gating is observed only when ions flow against the electrostatic potential gradient of the channel suggests a possible role for this porin in the regulation of charge distribution across the outer membrane and bacterial homeostasis (Song et al. 2015).