title: Amino acid substitutions in the pore affect the anomalous mole fraction effect of CaV1.2 channels.
abstract: 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.
authors.affiliation: Department of Cardiology, Renmin Hospital of Wuhan University,                     Wuhan, Hubei 430060, P.R. China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Li
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Hong
authors.initials: H
authors.lastname: Jiang
authors.forename: Guo-Feng
authors.initials: GF
authors.lastname: Gao
authors.forename: Blaise Z
authors.initials: BZ
authors.lastname: Peterson
authors.forename: Cong-Xin
authors.initials: CX
authors.lastname: Huang
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D018408:Patch-Clamp Techniques; D014162:Transfection
chemical_list: D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D001464:Barium; D002118:Calcium