Open AccessAmino acid substitutions in the pore affect the anomalous mole fraction effect of CaV1.2 channels
Author(s) -
Zhe Li,
He Huang,
Bo Yang,
Hong Jiang,
Guo Feng Gao,
Blaise Z. Peterson,
Chuanhe Huang
Publication year - 2012
Publication title -
molecular medicine reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.727
H-Index - 56
eISSN - 1791-3004
pISSN - 1791-2997
DOI - 10.3892/mmr.2012.1210
Subject(s) - divalent , mole fraction , permeation , chemistry , glycine , lysine , amino acid , mole , biophysics , ion channel , membrane potential , ion , voltage dependent calcium channel , stereochemistry , analytical chemistry (journal) , calcium , chromatography , biochemistry , membrane , biology , organic chemistry , receptor
The anomalous mole fraction effect (AMFE) is an important indicator of ion-ion interactions in the pore of voltage-gated Ca2+ channels (VGCCs). The residues at position 1144 that differ in several classes of VGCCs are important to the permeation of the pore. Phe-1144 (F, CaV1) was substituted with glycine (G, CaV2) and lysine (K, CaV3) and the effects of mutation on the voltage and concentration dependency of AMFE were observed. Whole-cell currents were recorded in external solutions with Ca2+ and Ba2+ at the indicated ratios with a total divalent cation concentration of 2, 10 or 20 mM, at holding potentials from -80 to -20 mV. Results showed the ratio of Ba2+ to Ca2+ currents determined at 2 mM to be different from that determined under higher concentrations for wild-type channels but this ratio was not different when tail currents were evoked at different potentials. AMFE was greatest at relatively positive potentials (-20 mV) and when the total divalent cation concentrations were kept low (2 mM). AMFE was attenuated for F/G while it was accentuated for F/K compared with wild-type, respectively. The results demonstrated that glycine and lysine substitutions of Phe-1144 affect AMFE through different mechanisms. Additionally, residues at position 1144 were shown to be major determinates of channel permeation of several classes of VGCCs.