ABCC7 p.Arg80Glu
| Predicted by SNAP2: | A: N (53%), C: D (66%), D: D (71%), E: D (53%), F: D (80%), G: D (59%), H: N (66%), I: D (59%), K: N (93%), L: D (53%), M: N (53%), N: N (57%), P: N (57%), Q: N (66%), S: N (72%), T: N (72%), V: D (53%), W: D (85%), Y: D (63%), |
| Predicted by PROVEAN: | A: N, C: N, D: N, E: N, F: D, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, S: N, T: N, V: N, W: D, Y: N, |
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[hide] Positive charges at the intracellular mouth of the... J Gen Physiol. 2006 Nov;128(5):535-45. Epub 2006 Oct 16. Aubin CN, Linsdell P
Positive charges at the intracellular mouth of the pore regulate anion conduction in the CFTR chloride channel.
J Gen Physiol. 2006 Nov;128(5):535-45. Epub 2006 Oct 16., [PMID:17043152]
Abstract [show]
Many different ion channel pores are thought to have charged amino acid residues clustered around their entrances. The so-called surface charges contributed by these residues can play important roles in attracting oppositely charged ions from the bulk solution on one side of the membrane, increasing effective local counterion concentration and favoring rapid ion movement through the channel. Here we use site-directed mutagenesis to identify arginine residues contributing important surface charges in the intracellular mouth of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel pore. While wild-type CFTR was associated with a linear current-voltage relationship with symmetrical solutions, strong outward rectification was observed after mutagenesis of two arginine residues (R303 and R352) located near the intracellular ends of the fifth and sixth transmembrane regions. Current rectification was dependent on the charge present at these positions, consistent with an electrostatic effect. Furthermore, mutagenesis-induced rectification was more pronounced at lower Cl(-) concentrations, suggesting that these mutants had a reduced ability to concentrate Cl(-) ions near the inner pore mouth. R303 and R352 mutants exhibited reduced single channel conductance, especially at negative membrane potentials, that was dependent on the charge of the amino acid residue present at these positions. However, the very low conductance of both R303E and R352E-CFTR could be greatly increased by elevating intracellular Cl(-) concentration. Modification of an introduced cysteine residue at position 303 by charged methanethiosulfonate reagents reproduced charge-dependent effects on current rectification. Mutagenesis of arginine residues in the second and tenth transmembrane regions also altered channel permeation properties, however these effects were not consistent with changes in channel surface charges. These results suggest that positively charged arginine residues act to concentrate Cl(-) ions at the inner mouth of the CFTR pore, and that this contributes to maximization of the rate of Cl(-) ion permeation through the pore.
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No. Sentence Comment
98 Mutations that did not alter I-V shape (R80E, R242E, R933E, and R1102E) also had no significant effect on unitary conductance (Fig. 4 D).
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ABCC7 p.Arg80Glu 17043152:98:40
status: NEW149 Under these conditions, current carried not only by wild-type CFTR, but also by each of the channel mutants R303E, R352E (Fig. 10), R80E, R242E, R933E, R1102E, and R352Q (not depicted) showed reversal potentials that were not significantly different from the calculated Cl- equilibrium potential (+33.4 mV).
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ABCC7 p.Arg80Glu 17043152:149:132
status: NEW206 Examples of similar data obtained from three to four patches for these channel variants and also for R80E, R242E, R352Q, R933E, and R1102E (not depicted).
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ABCC7 p.Arg80Glu 17043152:206:101
status: NEW