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.
N1 - Funding Information:
We gratefully acknowledge Kim Kluge and Maria Janecki for preparation of the mutants, Brian O'Rourke for review of the manuscript, Arthur Karlin for providing the MTS reagents, Dr. H. R. Guy for providing the coordinates of the P segment model, and Thomas Woolf for advice on structural modeling. This work was supported by National Institutes of Health grants P50 HL52307 to E. M. and R01 HL50411 to G. F. T., a Medical Research Council of Canada fellowship to N. C., and a Ramon Areces Foundation fellowship to M. T. P.-G.
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 -