TY - JOUR
T1 - Depth asymmetries of the pore-lining segments of the Na+ channel revealed by cysteine mutagenesis
AU - Chiamvimonvat, Nipavan
AU - Pérez-García, M. Teresa
AU - Ranjan, Ravi
AU - Marban, Eduardo
AU - Tomaselli, Gordon F.
PY - 1996/5
Y1 - 1996/5
N2 - We used serial cysteine mutagenesis to study the structure of the outer vestibule and selectivity region of the voltage-gated Na+ channel. The voltage dependence of Cd2+ block enabled us to determine the locations within the electrical field of cysteine-substituted mutants in the P segments of all four domains. The fractional electrical distances of the substituted cysteines were compared with the differential sensitivity to modification by sulfhydryl-specific modifying reagents. These experiments indicate that the P segment of domain II is external, while the domain IV P segment is displaced internally, compared with the first and third domain P segments. Sulfhydryls with a steep voltage dependence for Cd2+ block produced changes in monovalent cation selectivity; these included substitutions at the presumed selectivity filter, as well as residues in the domain IV P segment not previously recognized as determinants of selectivity. A new structural model is presented in which each of the P segments contribute unique loops that penetrate the membrane to varying depths to form the channel pore.
AB - We used serial cysteine mutagenesis to study the structure of the outer vestibule and selectivity region of the voltage-gated Na+ channel. The voltage dependence of Cd2+ block enabled us to determine the locations within the electrical field of cysteine-substituted mutants in the P segments of all four domains. The fractional electrical distances of the substituted cysteines were compared with the differential sensitivity to modification by sulfhydryl-specific modifying reagents. These experiments indicate that the P segment of domain II is external, while the domain IV P segment is displaced internally, compared with the first and third domain P segments. Sulfhydryls with a steep voltage dependence for Cd2+ block produced changes in monovalent cation selectivity; these included substitutions at the presumed selectivity filter, as well as residues in the domain IV P segment not previously recognized as determinants of selectivity. A new structural model is presented in which each of the P segments contribute unique loops that penetrate the membrane to varying depths to form the channel pore.
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U2 - 10.1016/S0896-6273(00)80127-0
DO - 10.1016/S0896-6273(00)80127-0
M3 - Article
C2 - 8630242
AN - SCOPUS:15844394267
SN - 0896-6273
VL - 16
SP - 1037
EP - 1047
JO - Neuron
JF - Neuron
IS - 5
ER -