ABCC7 p.Thr1115Ala
| Predicted by SNAP2: | A: N (87%), C: N (66%), D: D (66%), E: D (75%), F: D (63%), G: D (53%), H: D (75%), I: D (66%), K: D (85%), L: D (71%), M: D (53%), N: D (63%), P: D (75%), Q: D (63%), R: D (80%), S: N (82%), V: N (61%), W: D (80%), Y: D (71%), |
| Predicted by PROVEAN: | A: N, C: N, D: N, E: N, F: N, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, R: N, S: N, V: N, W: N, Y: N, |
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[hide] Relative contribution of different transmembrane s... Pflugers Arch. 2014 Mar;466(3):477-90. doi: 10.1007/s00424-013-1317-x. Epub 2013 Aug 20. Wang W, El Hiani Y, Rubaiy HN, Linsdell P
Relative contribution of different transmembrane segments to the CFTR chloride channel pore.
Pflugers Arch. 2014 Mar;466(3):477-90. doi: 10.1007/s00424-013-1317-x. Epub 2013 Aug 20., [PMID:23955087]
Abstract [show]
The membrane-spanning part of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel comprises 12 transmembrane (TM) alpha-helices, arranged in 2 symmetrical groups of 6. However, those TMs that line the channel pore are not completely defined. We used patch clamp recording to compare the accessibility of cysteine-reactive reagents to cysteines introduced into different TMs. Several residues in TM11 were accessible to extracellular and/or intracellular cysteine reactive reagents; however, no reactive cysteines were identified in TMs 5 or 11. Two accessible residues in TM11 (T1115C and S1118C) were found to be more readily modified from the extracellular solution in closed channels, but more readily modified from the intracellular solution in open channels, as previously reported for T338C in TM6. However, the effects of mutagenesis at S1118 (TM11) on a range of pore functional properties were relatively minor compared to the large effects of mutagenesis at T338 (TM6). Our results suggest that the CFTR pore is lined by TM11 but not by TM5 or TM7. Comparison with previous works therefore suggests that the pore is lined by TMs 1, 6, 11, and 12, suggesting that the structure of the open channel pore is asymmetric in terms of the contributions of different TMs. Although TMs 6 and 11 appear to undergo similar conformational changes during channel opening and closing, the influence of these two TMs on the functional properties of the narrowest region of the pore is clearly unequal.
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No. Sentence Comment
160 Conductance was also unaltered in T1115A.
X
ABCC7 p.Thr1115Ala 23955087:160:34
status: NEW167 Block by intracellular Au(CN)2 - was also significantly weakened in S1118A, S1118T, and T1115A compared to wild type, especially at hyperpolarized membrane potentials (Fig. 6); however, no apparent "U"-shape to the fractional current-voltage relationship was observed (Fig. 6b).
X
ABCC7 p.Thr1115Ala 23955087:167:88
status: NEW180 As proposed previously for TM6 residue T338 [42], the channel is shown as being in an "outward facing" configuration when closed (with T1115 and S1118 accessible from the outside), and switching to an "inward facing" configuration on opening (with T1115 and S1118 accessible from the inside) S1118A and T1115A, although this increase was much less than that observed in T338A (Fig. 7b).
X
ABCC7 p.Thr1115Ala 23955087:180:305
status: NEW183 Acetate permeability was slightly increased in S1118A and T1115A, but not significantly changed in S1118Q or S1118V (Fig. 8b).
X
ABCC7 p.Thr1115Ala 23955087:183:58
status: NEW207 The effects of the S1118A mutation on permeant anion (Au(CN)2 - ) binding (Fig. 6), permeability of the lyotropic SCN- anion (Fig. 7), and permeability of the organic acetate anion (Fig. 8) were qualitatively similar to, but generally smaller than, those of T338A, and in fact similar effects were seen in T1115A.
X
ABCC7 p.Thr1115Ala 23955087:207:306
status: NEW208 Neither S1118A nor T1115A significantly altered single channel conductance, although introduction of larger amino acid side chains in S1118Q and S1118V led to very small decreases in conductance (Fig. 5).
X
ABCC7 p.Thr1115Ala 23955087:208:19
status: NEW211 Reduction of side chain volume in S1118A and T1115A, like T338A, led to an increase in the relative permeability of the small organic anion acetate, consistent with an increase in the apparent diameter of the narrowest region of the pore [25, 26]; however, introduction of side chains with larger volume (S1118Q, S1118V) did not lead to a decrease in acetate permeability (Fig. 8).
X
ABCC7 p.Thr1115Ala 23955087:211:45
status: NEW217 One possible reason contributing to the minor functional effects observed in these experiments is that S1118A (and T1115A) might be considered relatively conservative mutations leading to only small changes in amino acid side chain volume.
X
ABCC7 p.Thr1115Ala 23955087:217:115
status: NEW