ABCMdb

ABCC7 p.Arg334Glu

ClinVar:	c.1000C>T , p.Arg334Trp D , Pathogenic c.1001G>T , p.Arg334Leu ? , not provided c.1001G>A , p.Arg334Gln ? , not provided
CF databases:	c.1000C>T , p.Arg334Trp D , CF-causing ; CFTR1: This mutation has been found in two Spanish CF chromosomes. One of the patients has the [delta]F508 mutation in the other chromosome and the other patient does not. We have not found this mutation on 30 normal chromosomes with the same haplotype, and in 88 CF chromosomes without the [delta]F508, and in 24 with the [delta]F508. The mutation destroys a MapI site and is easily identified by agarose gel electrophoresis after PCR with intron primers. c.1001G>A , p.Arg334Gln (CFTR1) ? , The above mutation was found by DGGE and direct sequencing in Caucasian patients. c.1001G>T , p.Arg334Leu (CFTR1) D , Missense mutation E334L was detected in a German CBAVD patient who is compound heterozygous for the R334L and I336K mutations.
Predicted by SNAP2:	A: D (91%), C: D (95%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (91%), I: D (95%), K: D (85%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (91%), S: D (91%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, G: N, H: N, I: D, K: N, L: N, M: N, N: N, P: N, Q: N, S: N, T: N, V: D, W: D, Y: D,

[switch to compact view]
Comments [show]

None has been submitted yet.

Publications
[hide] Molecular determinants and role of an anion bindin... J Physiol. 2003 Jun 1;549(Pt 2):387-97. Epub 2003 Apr 4. Gong X, Linsdell P
Molecular determinants and role of an anion binding site in the external mouth of the CFTR chloride channel pore.
J Physiol. 2003 Jun 1;549(Pt 2):387-97. Epub 2003 Apr 4., 2003-06-01 [PMID:12679372]

Abstract [show]
Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is blocked by highly lyotropic permeant anions which bind tightly within the pore. Here we show that several different substitutions of a positively charged amino acid residue, arginine R334, in the putative outer mouth of the CFTR pore, greatly reduce the block caused by lyotropic Au(CN)2- ions applied to the intracellular side of the channel. Fixed positive charge at this site appears to play a role in Au(CN)2- binding, as judged by multiple substitutions of differently charged amino acid side chains and also by the pH dependence of block conferred by the R334H mutant. However, non-charge-dependent effects also appear to contribute to Au(CN)2- binding. Mutation of R334 also disrupts the apparent electrostatic interaction between intracellular Au(CN)2- ions and extracellular permeant anions, an interaction which normally acts to relieve channel block. All six mutations studied at R334 significantly weakened this interaction, suggesting that arginine possesses a unique ability to coordinate ion-ion interactions at this site in the pore. Our results suggest that lyotropic anions bind tightly to a site in the outer mouth of the CFTR pore that involves interaction with a fixed positive charge. Binding to this site is also involved in coordination of multiple permeant anions within the pore, suggesting that anion binding in the outer mouth of the pore is an important aspect in the normal anion permeation mechanism.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
53 Block of wild-type, R334C-, R334E-, R334H-, R334K-, R334L- and R334Q-CFTR by 100 mM and 1 mM intracellular Au(CN)2 _ are compared in Fig. 4B. Login to comment
54 Block was affected in all mutants, depending on the ionic conditions used, but was particularly weakened in R334C, R334E and R334K (Fig. 5A-C). Login to comment
93 As noted by Smith et al. (2001), this effect was clearly charge dependent, being strongest in R334E and weak (but still significant) in R334K. Login to comment
111 Each of the mutations R334C, R334E and X. Gong and P. Linsdell394 J Physiol549.2 Figure 8. Login to comment
141 With either Cl_ or gluconate in the extracellular solution, Au(CN)2 _ block was most dramatically weakened in the mutants R334C, R334E and R334K, which involve replacement of the positively charged arginine side chain with one neutral side chain (cysteine), one negatively charged side chain (glutamate) and one positively charged side chain Anion binding site in the CFTR pore outer mouthJ Physiol 549.2 395 (lysine). Login to comment

[hide] Direct and indirect effects of mutations at the ou... J Membr Biol. 2007 Apr;216(2-3):129-42. Epub 2007 Aug 3. Zhou JJ, Fatehi M, Linsdell P
Direct and indirect effects of mutations at the outer mouth of the cystic fibrosis transmembrane conductance regulator chloride channel pore.
J Membr Biol. 2007 Apr;216(2-3):129-42. Epub 2007 Aug 3., [PMID:17673962]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel pore is thought to contain multiple binding sites for permeant and impermeant anions. Here, we investigate the effects of mutation of different positively charged residues in the pore on current inhibition by impermeant Pt(NO(2)) (4) (2-) and suramin anions. We show that mutations that remove positive charges (K95, R303) influence interactions with intracellular, but not extracellular, Pt(NO(2))(4)(2-) ions, consistent with these residues being situated within the pore inner vestibule. In contrast, mutation of R334, supposedly located in the outer vestibule of the pore, affects block by both extracellular and intracellular Pt(NO(2))(4)(2-). Inhibition by extracellular Pt(NO(2))(4)(2-) requires a positive charge at position 334, consistent with a direct electrostatic interaction resulting in either open channel block or surface charge screening. In contrast, inhibition by intracellular Pt(NO(2))(4)(2-) is weakened in all R334-mutant forms of the channel studied, inconsistent with a direct interaction. Furthermore, mutation of R334 had similar effects on block by intracellular suramin, a large organic molecule that is apparently unable to enter deeply into the channel pore. Mutation of R334 altered interactions between intracellular Pt(NO(2))(4)(2-) and extracellular Cl(-) but not those between intracellular Pt(NO(2))(4)(2-) and extracellular Pt(NO(2))(4)(2-). We propose that while the positive charge of R334 interacts directly with extracellular anions, mutation of this residue also alters interactions with intracellular anions by an indirect mechanism, due to mutation-induced conformational changes in the protein that are propagated some distance from the site of the mutation in the outer mouth of the pore.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
85 Figure 3 shows the blocking effects of internally applied Pt(NO2)4 2À in six different channel mutants (R334C, R334E, R334H, R334K, R334L, R334Q) under conditions of both low (Fig. 3a) and high (Fig. 3b) extracellular ClÀ concentration. Login to comment
90 With low extracellular ClÀ concentrations, the Kd for Pt(NO2)4 2À block (at 0 mV) was significantly increased in all six R334 mutants studied (Fig. 5a), although it is clear that R334C and R334E had far greater effects on Kd compared to other amino acid substitutions. Login to comment
91 With elevated extracellular ClÀ , the Kd(0) was significantly increased only in R334C and R334E; not significantly altered in R334K, R334L and R334Q; and significantly decreased in R334H (Fig. 5b). Login to comment
106 Comparison of the mean Kd estimated for suramin (at 0 mV) shows that R334C, R334E, R334K, R334L and R334Q were all associated with weakened suramin block, with only R334H failing to significantly affect suramin block (Fig. 7). Login to comment
107 Suramin block was particularly weakened in R334C and R334E (Figs. 6, 7) such that the profiles of mutation effects on block by internal Pt(NO2)4 2À and suramin are very similar. Login to comment
129 Mean of data from three to eight patches. Fitted lines are to equation 1 as described in Figure 1 for wild type and R334Q and with the following parameters for other channel variants: R334C 4 mM external ClÀ , Kd(0) = 1362 lM, zd = À0.295; R334C 154 mM external ClÀ , Kd(0) = 836 lM, zd = À0.219; R334E 4 mM external ClÀ , Kd(0) = 759 lM, zd = À0.376; R334E 154 mM external ClÀ , Kd(0) = 564 lM, zd = À0.173; R334H 4 mM external ClÀ , Kd(0) = 140 lM, zd = À0.166; R334H 154 mM external ClÀ , Kd(0) = 119 lM, zd = À0.149; R334K 4 mM external ClÀ , Kd(0) = 143 lM, zd = À0.314; R334K 154 mM external ClÀ , Kd(0) = 317 lM, zd = À0.374; R334L 4 mM external ClÀ , Kd(0) = 176 lM, zd = À0.258; R334L 154 mM external ClÀ , Kd(0) = 284 lM, zd = À0.366 extracellular Pt(NO2)4 2À by normalizing current amplitude at the hyperpolarized extreme of the voltage range studied, -80 mV (Fig. 10b). Login to comment
159 These plots represent mean data from four to seven patches. Fitted lines are to equation 1 with the following parameters: wild type, Kd(0) = 2.51 lM, zd = À0.042; R334C, Kd(0) = 18.5 lM, zd = À0.056; R334E, Kd(0) = 25.0 lM, zd = À0.107; R334H, Kd(0) = 3.10 lM, zd = À0.085; R334K, Kd(0) = 6.31 lM, zd = À0.232; R334L, Kd(0) = 4.08 lM, zd = À0.061; R334Q, Kd(0) = 6.64 lM, zd = À0.239 with our previous suggestion that intracellular Au(CN)2 À blocks the channel by interacting directly with R334, several reasons prompt us to suggest that Pt(NO2)4 2À does not interact directly with the arginine side chain at this position. Login to comment
162 Thus, while Pt(NO2)4 2À block is particularly weak in R334C and R334E (Figs. 3-5), there is no strong correlation between the apparent affinity of Pt(NO2)4 2À block and the nature of the side chain present at position 334. Login to comment
166 The similar effects of mutations on block by intracellular suramin and intracellular Pt(NO2)4 2À - in particular, the strong effects of R334C and R334E on the inhibitory effects of both blockers - suggest that these mutations affect suramin block and Pt(NO2)4 2À block by a common mechanism. Login to comment
221 However, disruption of the effects of intracellular blockers is particularly pronounced in R334C and R334E (Figs. 5, 7). Login to comment
222 Currently, we have no explanation as to why R334C and R334E have so much more dramatic effects on block by intracellular Pt(NO2)4 2À and suramin than other R334 mutations. Login to comment
228 ), R334E (5), R334H (j), R334K (), R334L (h), R334Q (u); c wild type (d), K95Q (m), R303Q (Å). Login to comment

[hide] Cystic fibrosis transmembrane conductance regulato... J Cell Biol. 1998 Nov 2;143(3):645-57. Jiang Q, Mak D, Devidas S, Schwiebert EM, Bragin A, Zhang Y, Skach WR, Guggino WB, Foskett JK, Engelhardt JF
Cystic fibrosis transmembrane conductance regulator-associated ATP release is controlled by a chloride sensor.
J Cell Biol. 1998 Nov 2;143(3):645-57., 1998-11-02 [PMID:9813087]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel that is defective in cystic fibrosis, and has also been closely associated with ATP permeability in cells. Using a Xenopus oocyte cRNA expression system, we have evaluated the molecular mechanisms that control CFTR-modulated ATP release. CFTR-modulated ATP release was dependent on both cAMP activation and a gradient change in the extracellular chloride concentration. Activation of ATP release occurred within a narrow concentration range of external Cl- that was similar to that reported in airway surface fluid. Mutagenesis of CFTR demonstrated that Cl- conductance and ATP release regulatory properties could be dissociated to different regions of the CFTR protein. Despite the lack of a need for Cl- conductance through CFTR to modulate ATP release, alterations in channel pore residues R347 and R334 caused changes in the relative ability of different halides to activate ATP efflux (wtCFTR, Cl >> Br; R347P, Cl >> Br; R347E, Br >> Cl; R334W, Cl = Br). We hypothesize that residues R347 and R334 may contribute a Cl- binding site within the CFTR channel pore that is necessary for activation of ATP efflux in response to increases of extracellular Cl-. In summary, these findings suggest a novel chloride sensor mechanism by which CFTR is capable of responding to changes in the extracellular chloride concentration by modulating the activity of an unidentified ATP efflux pathway. This pathway may play an important role in maintaining fluid and electrolyte balance in the airway through purinergic regulation of epithelial cells. Insight into these molecular mechanisms enhances our understanding of pathogenesis in the cystic fibrosis lung.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
321 The number of oocytes (N) compiled for each mutant are given with the number of independent experiments for wtCFTR ϭ 3, R347P ϭ 2, R334E ϭ 3, R334W ϭ 2, and water ϭ 3. Login to comment

[hide] CFTR: a cysteine at position 338 in TM6 senses a p... Biophys J. 2004 Dec;87(6):3826-41. Epub 2004 Sep 10. Liu X, Zhang ZR, Fuller MD, Billingsley J, McCarty NA, Dawson DC
CFTR: a cysteine at position 338 in TM6 senses a positive electrostatic potential in the pore.
Biophys J. 2004 Dec;87(6):3826-41. Epub 2004 Sep 10., [PMID:15361410]

Abstract [show]
We investigated the accessibility to protons and thiol-directed reagents of a cysteine substituted at position 338 in transmembrane segment 6 (TM6) of CFTR to test the hypothesis that T338 resides in the pore. Xenopus oocytes expressing T338C CFTR exhibited pH-dependent changes in gCl and I-V shape that were specific to the substituted cysteine. The apparent pKa of T338C CFTR was more acidic than that expected for a cysteine or similar simple thiols in aqueous solution. The pKa was shifted toward alkaline values when a nearby positive charge (R334) was substituted with neutral or negatively charged residues, consistent with the predicted influence of the positive charge of R334, and perhaps other residues, on the titration of a cysteine at 338. The relative rates of chemical modification of T338C CFTR by MTSET+ and MTSES- were also altered by the charge at 334. These observations support a model for CFTR that places T338 within the anion conduction path. The apparent pKa of a cysteine substituted at 338 and the relative rates of reaction of charged thiol-directed reagents provide a crude measure of a positive electrostatic potential that may be due to R334 and other residues near this position in the pore.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
184 To investigate the effect of charge at position 334 on the titration behavior of T338C CFTR, we examined the conductance of oocytes expressing double mutants, T338C/R334A, T338C/R334E, and T338C/R334D CFTR. Login to comment
185 Shown in Fig. 8 A are representative titration curves for the conductance for T338C CFTR and two of these double mutants (n ¼ 5 each). Login to comment
187 The substitution of acidic residues, however, did not result in a large additional shift of the apparent pKa to more alkaline values (8.84 6 0.05 for T338C/R334D CFTR, n ¼ 4 and 8.96 6 0.08 for T338C/R334E CFTR, n ¼ 5). Login to comment
221 FIGURE 8 The pH-induced changes in the conductances of oocytes expressing T338C/R334A, T338C/R334E, T338H, or T338H/R334C CFTR. Login to comment
222 (A) Sample titration curves of conductances of oocytes expressing T338C CFTR (solid circles), T338C/R334A (open squares), or T338C/ R334E CFTRs (shaded triangles). Login to comment
342 A comparison of T338C/R334A (pKa ¼ 8.8) with T338C/R334E (pKa ¼ 8.9), would suggest a further change in Cq o of ;ÿ6 mV. Login to comment
360 It would not be surprising to find that the thiolate- arginine ion pair of T338C/R334 was closer together than the thiolate-glutamic acid pair of T338C/R334E, even if there were no major change in structure that accompanied the mutations. Login to comment
188 The substitution of acidic residues, however, did not result in a large additional shift of the apparent pKa to more alkaline values (8.84 6 0.05 for T338C/R334D CFTR, n &#bc; 4 and 8.96 6 0.08 for T338C/R334E CFTR, n &#bc; 5). Login to comment
223 (A) Sample titration curves of conductances of oocytes expressing T338C CFTR (solid circles), T338C/R334A (open squares), or T338C/ R334E CFTRs (shaded triangles). Login to comment
344 A comparison of T338C/R334A (pKa &#bc; 8.8) with T338C/R334E (pKa &#bc; 8.9), would suggest a further change in Cq o of ;6 mV. Login to comment
361 It would not be surprising to find that the thiolate- arginine ion pair of T338C/R334 was closer together than the thiolate-glutamic acid pair of T338C/R334E, even if there were no major change in structure that accompanied the mutations. Login to comment

[hide] Cystic fibrosis transmembrane conductance regulato... Biophys J. 1998 Mar;74(3):1320-32. Mansoura MK, Smith SS, Choi AD, Richards NW, Strong TV, Drumm ML, Collins FS, Dawson DC
Cystic fibrosis transmembrane conductance regulator (CFTR) anion binding as a probe of the pore.
Biophys J. 1998 Mar;74(3):1320-32., [PMID:9512029]

Abstract [show]
We compared the effects of mutations in transmembrane segments (TMs) TM1, TM5, and TM6 on the conduction and activation properties of the cystic fibrosis transmembrane conductance regulator (CFTR) to determine which functional property was most sensitive to mutations and, thereby, to develop a criterion for measuring the importance of a particular residue or TM for anion conduction or activation. Anion substitution studies provided strong evidence for the binding of permeant anions in the pore. Anion binding was highly sensitive to point mutations in TM5 and TM6. Permeability ratios, in contrast, were relatively unaffected by the same mutations, so that anion binding emerged as the conduction property most sensitive to structural changes in CFTR. The relative insensitivity of permeability ratios to CFTR mutations was in accord with the notion that anion-water interactions are important determinants of permeability selectivity. By the criterion of anion binding, TM5 and TM6 were judged to be likely to contribute to the structure of the anion-selective pore, whereas TM1 was judged to be less important. Mutations in TM5 and TM6 also dramatically reduced the sensitivity of CFTR to activation by 3-isobutyl 1-methyl xanthine (IBMX), as expected if these TMs are intimately involved in the physical process that opens and closes the channel.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
229 Hipper et al. (1995) reported that the mutations R334E, R334H, K335E, K335H, R347E, and R347H did not alter CFTR conduction properties, but careful inspection of the data presented revealed that the level of CFTR expression was very low so that altered properties of mutant CFTRs might have been easily obscured. Login to comment

[hide] Mutations in the putative pore-forming domain of C... FEBS Lett. 1995 Nov 6;374(3):312-6. Hipper A, Mall M, Greger R, Kunzelmann K
Mutations in the putative pore-forming domain of CFTR do not change anion selectivity of the cAMP activated Cl- conductance.
FEBS Lett. 1995 Nov 6;374(3):312-6., [PMID:7589561]

Abstract [show]
Cystic fibrosis transmembrane conductance regulator (CFTR) apparently forms Cl- channels in apical membranes of secretory epithelial cells. A detailed model describes molecular structure and biophysical properties of CFTR and the impact of various mutations as they occur in cystic fibrosis. In the present report mutations were introduced into the putative 6th alpha-helical transmembrane pore forming domain of CFTR. The mutants were subsequently expressed in Xenopus oocytes by injection of the respective cRNAs. Whole cell (wc) conductances could be reversibly activated by IBMX (1 nmol/l) only in oocytes injected with wild-type (wt) or mutant CFTR but not in oocytes injected with water or antisense CFTR. The activated conductance was partially inhibited by (each 100 mumol/l) DIDS (27%) and glibenclamide (77%), but not by 10 mumol/l NPPB. The following mutations were examined: K335E, R347E, R334E, K335H, R347H, R334H. They did not measurably change the wt-CFTR anion permeability (P) and we conductance (G) sequence of: PCl- > PBr- > P1- and GCl- > GBr- > G1-, respectively. Moreover, anomalous mole fraction behavior for the cAMP activated current could not be detected: neither in wt-CFTR nor in R347E-CFTR. Various mutants for which positively charged amino acids were replaced by histidines (K335H, R347H, R334H) did not show pH sensitivity of the IBMX activated wc conductance. We, therefore, cannot confirm previous results. CFTR might have a different molecular structure than previously suggested or it might act as a regulator of ion conductances.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
6 The following mutations were examined: K335E, R347E, R334E, K335H, R347H, R334H. Login to comment
32 Synthesis of mutated CFTR-cDNA was induced by annealing of ampicillin repair oligonucleotide and oligonucleotide primers carrying the respective mutation changing positively charged to negatively charged amino acids (R334E, R347E, K335E) or replacing R and K at these positions by histidines (R334H, R347H, K335H). Login to comment
80 Next, positively charged amino acids R334, R347, K335 located in the putative 6th pore forming transmembrane a-helical domain of CFTR, were exchanged by histidines (R334H, R347H, K335H) or by the negatively charged glutamate (R334E, R347E, K335E). Login to comment
81 Wc conductances were activated significantly by IBMX in all 6 mutants but to variable degrees (AG in/.tS): 3.2 + 0.6 (R334E, n = 20), 2.7 + 0.6 (R334H, n = 13), 7.1 + 0.9 (K335E, n-- 20), 2.8 + 0.7 (K335H, n = 10), 3.2 + 0.04 (R347E, n = 32) and 1.8 + 0.3 (R347H, n = 10). Login to comment
90 It was 2.2 + 0.3 (wt CFTR, n = 17) and 2.0 _+0.2 (R334E, n -- 19), respectively. Login to comment
108 In the present study we repeated some of the published (K335E, R347E, R347H) and performed additional mutations (R334E, R334H, K335H) which are all located in the putative sixth transmembrane domain and overexpressed the respective CFTRs in oocytes. Login to comment

[hide] Maximization of the rate of chloride conduction in... Arch Biochem Biophys. 2004 Jun 1;426(1):78-82. Gong X, Linsdell P
Maximization of the rate of chloride conduction in the CFTR channel pore by ion-ion interactions.
Arch Biochem Biophys. 2004 Jun 1;426(1):78-82., [PMID:15130785]

Abstract [show]
Multi-ion pore behaviour has been identified in many Cl(-) channel types but its biophysical significance is uncertain. Here, we show that mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel that disrupt anion-anion interactions within the pore are associated with drastically reduced single channel conductance. These results are consistent with models suggesting that rapid Cl(-) permeation in CFTR results from repulsive ion-ion interactions between Cl(-) ions bound concurrently inside the pore. Naturally occurring mutations that disrupt these interactions can result in cystic fibrosis.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
35 Results and discussion Previously we characterized the properties of six different R334 mutants (R334C, R334E, R334H, R334K, R334L, and R334Q) [19]. Login to comment
65 (A) Unitary current-voltage relationships for each of the channel variants shown in Fig. 1: (d) wild type, (r) R334C, (j) R334E, (}) R334H, (s) R334K, () R334L, (.) Login to comment