ABCMdb

ABCC7 p.Glu1126Arg

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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Publications
[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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118 Fig. S6 shows representative I-V plots of double mutants R104E/ E116R- and R117E/E1126R-CFTR and their rectification ratio. Login to comment
224 Tab l e 1 Reversal potentials of WT-CFTR and mutants in ND96 bath solution CFTR n Vrev mV WT 14 &#e032;27.75 &#b1; 0.78 R334A 6 &#e032;12.15 &#b1; 1.64a R117A 6 &#e032;22.51 &#b1; 0.85a E116R 5 &#e032;21.45 &#b1; 1.14a K114D 5 &#e032;24.68 &#b1; 3.22 D110R 5 &#e032;27.64 &#b1; 3.29 R104E 5 &#e032;21.15 &#b1; 1.08a R899C 4 &#e032;25.30 &#b1; 3.94 D891C 6 &#e032;25.81 &#b1; 2.44 K892E 5 &#e032;23.70 &#b1; 3.62 E1124R 5 &#e032;18.32 &#b1; 0.43a E1126R 5 &#e032;20.67 &#b1; 3.16b R117E/E1126R 6 &#e032;23.06 &#b1; 1.37b R104E/E116R 6 &#e032;27.17 &#b1; 1.08 Values are mean &#b1; SEM. Login to comment
380 Sample current traces for both E1126R- and R117E/ E1126R-CFTR are shown in Fig. 12 A. Login to comment
403 We also compared the fractional burst duration represented by s1, s2, and f states for E1126R- and R117E/E1126R-CFTR and found that E1126R exhibited a significantly higher fraction of both s1 and s2 states than WT, whereas the distribution for double mutant R117E/E1126R-CFTR was similar to WT-CFTR, exhibiting mainly the f state (a nearly complete rescue; Fig. 12 D). Login to comment
405 E1126R-CFTR mainly opened to the full open state but with frequent brief transitions to the s1 and s2 states. Login to comment
406 R117E/E1126R-CFTR opened to a full open state much more often compared with R117A-CFTR (Fig. 2). Login to comment
407 Mean burst duration for both E1126R- and R117E/ E1126R-CFTR are summarized in Fig. 12 B. Login to comment
408 The mean burst duration of R117E/E1126R-CFTR was significantly longer than that of R117A- and R117C-CFTR. Login to comment
410 (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). Login to comment
412 #, 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. Login to comment
417 (D) Mean fraction of open burst duration is plotted for each open conductance state of E1126R- and R117E/E1126R-CFTR. Login to comment