ABCC7 p.Glu1126Cys
| Predicted by SNAP2: | A: N (78%), C: N (53%), D: D (53%), F: D (85%), G: N (61%), H: D (85%), I: D (66%), K: D (75%), L: D (63%), M: D (80%), N: D (63%), P: D (71%), Q: N (53%), R: D (80%), S: N (61%), T: N (53%), V: N (53%), W: D (91%), Y: D (85%), |
| Predicted by PROVEAN: | A: N, C: N, D: 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, T: N, V: N, W: D, Y: N, |
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[hide] Three charged amino acids in extracellular loop 1 ... J Gen Physiol. 2014 Aug;144(2):159-79. doi: 10.1085/jgp.201311122. Epub 2014 Jul 14. Cui G, Rahman KS, Infield DT, Kuang C, Prince CZ, McCarty NA
Three charged amino acids in extracellular loop 1 are involved in maintaining the outer pore architecture of CFTR.
J Gen Physiol. 2014 Aug;144(2):159-79. doi: 10.1085/jgp.201311122. Epub 2014 Jul 14., [PMID:25024266]
Abstract [show]
The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) bears six extracellular loops (ECL1-6); ECL1 is the site of several mutations associated with CF. Mutation R117H has been reported to reduce current amplitude, whereas D110H, E116K, and R117C/L/P may impair channel stability. We hypothesized that these amino acids might not be directly involved in ion conduction and permeation but may contribute to stabilizing the outer vestibule architecture in CFTR. We used cRNA injected oocytes combined with electrophysiological techniques to test this hypothesis. Mutants bearing cysteine at these sites were not functionally modified by extracellular MTS reagents and were blocked by GlyH-101 similarly to WT-CFTR. These results suggest that these three residues do not contribute directly to permeation in CFTR. In contrast, mutants D110R-, E116R-, and R117A-CFTR exhibited instability of the open state and significantly shortened burst duration compared with WT-CFTR and failed to be locked into the open state by AMP-PNP (adenosine 5'-(beta,gamma-imido) triphosphate); charge-retaining mutants showed mainly the full open state with comparably longer open burst duration. These interactions suggest that these ECL1 residues might be involved in maintaining the outer pore architecture of CFTR. A CFTR homology model suggested that E116 interacts with R104 in both the closed and open states, D110 interacts with K892 in the fully closed state, and R117 interacts with E1126 in the open state. These interactions were confirmed experimentally. The results suggest that D110, E116, and R117 may contribute to stabilizing the architecture of the outer pore of CFTR by interactions with other charged residues.
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No. Sentence Comment
402 The single-channel amplitudes of R117C- and R117C/E1126C-CFTR were slightly, but significantly, smaller than that of WT-CFTR (Fig. 12 C).
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ABCC7 p.Glu1126Cys 25024266:402:50
status: NEW410 (A) Representative single-channel current traces of E1126R-, R117E/E1126R-, R117C-, and R117C/E1126C-CFTR recorded under the same experimental conditions as Fig. 2 and their all-points amplitude histograms (right).
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ABCC7 p.Glu1126Cys 25024266:410:94
status: NEW412 #, P < 0.01 indicates a significant difference between WTand R117C-CFTR; **, P < 0.01 indicates a significant difference between WTand E1126R-CFTR, between R117C and R117E/E1126R-CFTR, and between R117C and R117C/E1126C.
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ABCC7 p.Glu1126Cys 25024266:412:213
status: NEW431 R117C/E1126C-CFTR exhibited very brief openings to multiple open states, including s1, s2, and f, with significantly shorter mean burst duration compared with R117C-CFTR (P < 0.01), likely caused by mutual repulsion by the partial negative charges at the two cysteines, leading to unstable open states (Fig. 12, A and B).
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ABCC7 p.Glu1126Cys 25024266:431:6
status: NEW