Abstract
Neurotransmitter binding to Cys-loop receptors promotes a prodigious transmembrane flux of several million ions/s, but to date, structural determinants of ion flux have been identified flanking the membrane-spanning region. Using x-ray crystallography, sequence analysis, and single-channel recording, we identified a novel determinant of ion conductance near the point of entry of permeant ions. Co-crystallization of acetylcholine-binding protein with sulfate anions revealed coordination of SO42- with a ring of lysines at a position equivalent to 24 Å above the lipid membrane in homologous Cys-loop receptors. Analysis of multiple sequence alignments revealed that residues equivalent to the ring of lysines are negatively charged in cation-selective receptors but are positively charged in anion-selective receptors. Charge reversal of side chains at homologous positions in the nicotinic receptor from the motor end plate decreases unitary conductance up to 80%. Selectivity filters stemming from transmembrane α-helices have similar pore diameters and compositions of amino acids. These findings establish that when the channel opens under a physiological electrochemical gradient, permeant ions are initially stabilized within the extracellular vestibule of Cys-loop receptors, and this stabilization is a major determinant of ion conductance.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 36066-36070 |
| Number of pages | 5 |
| Journal | Journal of Biological Chemistry |
| Volume | 283 |
| Issue number | 52 |
| DOIs | |
| State | Published - Dec 26 2008 |
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ASJC Scopus subject areas
- Biochemistry
- Cell Biology
- Molecular Biology
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An ion selectivity filter in the extracellular domain of Cys-loop receptors reveals determinants for ion conductance. / Hansen, Scott B.; Wang, Hai Long; Taylor, Palmer; Sine, Steven M.
In: Journal of Biological Chemistry, Vol. 283, No. 52, 26.12.2008, p. 36066-36070.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - An ion selectivity filter in the extracellular domain of Cys-loop receptors reveals determinants for ion conductance
AU - Hansen, Scott B.
AU - Wang, Hai Long
AU - Taylor, Palmer
AU - Sine, Steven M
PY - 2008/12/26
Y1 - 2008/12/26
N2 - Neurotransmitter binding to Cys-loop receptors promotes a prodigious transmembrane flux of several million ions/s, but to date, structural determinants of ion flux have been identified flanking the membrane-spanning region. Using x-ray crystallography, sequence analysis, and single-channel recording, we identified a novel determinant of ion conductance near the point of entry of permeant ions. Co-crystallization of acetylcholine-binding protein with sulfate anions revealed coordination of SO42- with a ring of lysines at a position equivalent to 24 Å above the lipid membrane in homologous Cys-loop receptors. Analysis of multiple sequence alignments revealed that residues equivalent to the ring of lysines are negatively charged in cation-selective receptors but are positively charged in anion-selective receptors. Charge reversal of side chains at homologous positions in the nicotinic receptor from the motor end plate decreases unitary conductance up to 80%. Selectivity filters stemming from transmembrane α-helices have similar pore diameters and compositions of amino acids. These findings establish that when the channel opens under a physiological electrochemical gradient, permeant ions are initially stabilized within the extracellular vestibule of Cys-loop receptors, and this stabilization is a major determinant of ion conductance.
AB - Neurotransmitter binding to Cys-loop receptors promotes a prodigious transmembrane flux of several million ions/s, but to date, structural determinants of ion flux have been identified flanking the membrane-spanning region. Using x-ray crystallography, sequence analysis, and single-channel recording, we identified a novel determinant of ion conductance near the point of entry of permeant ions. Co-crystallization of acetylcholine-binding protein with sulfate anions revealed coordination of SO42- with a ring of lysines at a position equivalent to 24 Å above the lipid membrane in homologous Cys-loop receptors. Analysis of multiple sequence alignments revealed that residues equivalent to the ring of lysines are negatively charged in cation-selective receptors but are positively charged in anion-selective receptors. Charge reversal of side chains at homologous positions in the nicotinic receptor from the motor end plate decreases unitary conductance up to 80%. Selectivity filters stemming from transmembrane α-helices have similar pore diameters and compositions of amino acids. These findings establish that when the channel opens under a physiological electrochemical gradient, permeant ions are initially stabilized within the extracellular vestibule of Cys-loop receptors, and this stabilization is a major determinant of ion conductance.
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U2 - 10.1074/jbc.C800194200
DO - 10.1074/jbc.C800194200
M3 - Article
C2 - 18940802
AN - SCOPUS:61349137676
VL - 283
SP - 36066
EP - 36070
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 52
ER -