ABCMdb

ABCC7 p.Arg242Glu

Predicted by SNAP2:	A: D (71%), C: D (80%), D: D (91%), E: D (71%), F: D (91%), G: D (85%), H: N (72%), I: D (85%), K: N (93%), L: D (71%), M: N (66%), N: D (63%), P: D (91%), Q: N (72%), S: D (75%), T: D (59%), V: D (85%), W: D (91%), Y: D (71%),
Predicted by PROVEAN:	A: N, C: D, D: D, E: N, F: D, G: D, H: N, I: D, K: N, L: N, M: N, N: N, P: D, Q: N, S: N, T: N, V: N, W: D, Y: D,

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Publications
[hide] Topogenesis of cystic fibrosis transmembrane condu... Biochemistry. 1999 Apr 27;38(17):5471-7. Chen M, Zhang JT
Topogenesis of cystic fibrosis transmembrane conductance regulator (CFTR): regulation by the amino terminal transmembrane sequences.
Biochemistry. 1999 Apr 27;38(17):5471-7., 1999-04-27 [PMID:10220334]

Abstract [show]
Cystic fibrosis transmembrane conductance regulator (CFTR) is a member of the ATP-binding cassette (ABC) transport superfamily. CFTR folding and assembly appear to involve several events occurred in the cytosol and ER. Misfolding of CFTR causes cystic fibrosis, and thus, understanding the folding mechanism of CFTR is extremely important. Recently, detailed study of membrane insertion process suggests that the first two transmembrane (TM) segments of CFTR have two distinct but independent mechanisms to ensure the correct membrane folding of its amino terminal end [Lu, Y., Xiong, X., Helm, A., Kimani, K., Bragin, A., Skach, W. R. (1998) J. Biol. Chem. 273, 568-576]. To understand how other TM segments are ensured to insert into membranes correctly, we investigated the topogenesis of TM3 and TM4 of CFTR in a cell-free expression system. We found that the correct membrane insertion of TM3 and TM4 of CFTR was ensured by their flanking amino acid sequences and controlled by the correct membrane insertion of their preceding TM1 and TM2. Thus, correct membrane insertion and folding of TM1 and TM2 play an essential role in the membrane insertion and folding of the subsequent TM segments of CFTR.

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No. Sentence Comment
47 Primers carrying various mutations are 5'-AATCTGGAGGTTGTTAAAGGCGTC-3' (E217R/Q220K), 5'-CATCATTTCCCCTAGCCC-3' (R242E), 5'-CT- GATCTTCGTAATTCATCATCAT-3' (K246N/R248E), and 5'-TCCCAGCTTCCTGATCT-3' (R251E). Login to comment
49 The resulting constructs were named CFTR-N4R(E217R/Q220K), CFTR-N4R(R242E), CFTR-N4R(K246N/R248E), CFTR-N4R(R251E), CFTR-N4R(-8), and CFTR-N4R(-5). Login to comment
53 The final DNA clones were named CF-TM3,4R, CF-TM3,4R(E217R/Q220K), CF-TM3,4R(-8), and CF-TM3,4R(-5), respectively. To engineer R242E and K246N/R248E mutations into CF-TM3,4R, an EcoRI-EcoNI fragment encoding TM3 and part of TM4 was released from CF-TM3,4R and used to replace the amino terminal-encoding sequence in CFTR-N4R(R242E) and CFTR-N4R(K246N/R248E). Login to comment
54 The resulting constructs were named CF-TM3,4R(R242E) and CF-TM3,4R(K246N/R248E), respectively. To replace TM1 and TM2 of CFTR with that of Pgp, CFTR-N4R(-8) was linearized with XbaI, treated with Klenow DNA polymerase supplemented with dNTP in the absence of dGTP to avoid filling at the G position, and then digested with HindIII. The XbaI-HindIII fragment from CFTR-N4R(-8) and an EcoRI-NciI fragment encoding TM1 and TM2 of Pgp from pGPGP-N3 (12) were ligated into a pGEM-4z vector digested with EcoRI and HindIII. The resulting construct was named P1,2CF3,4R(-8). Login to comment
72 The mutant molecules used were CF-TM3,4R(E217R/ Q220K), CF-TM3,4R(R242E), and CF-TM3,4R(K246N/ R248E). Login to comment

[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). Login to comment
149 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). Login to comment
206 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). Login to comment