ABCC7 p.Arg352His
| ClinVar: |
c.1054C>T
,
p.Arg352Trp
D
, Likely pathogenic
c.1055G>A , p.Arg352Gln D , Pathogenic |
| CF databases: |
c.1055G>A
,
p.Arg352Gln
D
, CF-causing ; CFTR1: This missense mutation, at nucleotide position 1187 (G to A) in exon 7, has been detected in an Italian CF patient through DGGE and direct sequencing. The mutation generates an Arg to Gln substitution (R352Q) and creates a novel DdeI restriction site in the mutated allele. This mutation has been detected in a PS patient (paternal chromosome), associated with the haplotype A; the maternal chromosome carries a still uncharacterized mutation. It was found in one of 60 non-[delta] Italian CF chromosomes.
c.1054C>G , p.Arg352Gly (CFTR1) ? , c.1054C>T , p.Arg352Trp (CFTR1) ? , The mutation was detected by SSCP/heteroduplex analysis and identified by direct DNA sequencing. The mutation was seen in a boy referred by West Midlands Regional Genetics Service, and whose other CF mutation was [delta]F508. We have seen it only once in over 150 samples tested. |
| Predicted by SNAP2: | A: D (91%), C: D (95%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (91%), K: D (85%), L: D (91%), M: D (95%), N: D (95%), P: D (95%), Q: D (59%), S: D (95%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%), |
| 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, S: N, T: N, V: N, W: N, Y: N, |
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[hide] Arg352 is a major determinant of charge selectivit... Biochemistry. 1999 Apr 27;38(17):5528-37. Guinamard R, Akabas MH
Arg352 is a major determinant of charge selectivity in the cystic fibrosis transmembrane conductance regulator chloride channel.
Biochemistry. 1999 Apr 27;38(17):5528-37., 1999-04-27 [PMID:10220340]
Abstract [show]
The cystic fibrosis transmembrane conductance regulator forms an anion-selective channel. We previously showed that charge selectivity, the ability to discriminate between anions and cations, occurs near the cytoplasmic end of the channel. The molecular determinants of charge selectivity, however, are unknown. We investigated the role of Arg352, a residue flanking the predicted cytoplasmic end of the M6 segment, in the mechanism of charge selectivity. We determined the Cl- to Na+ permeability ratio (PCl/PNa) from the reversal potential measured in a 10-fold NaCl gradient. For the wild type, PCl/PNa was 36 (range of 28-51). For the R352H mutant, PCl/PNa was dependent on cytoplasmic pH. At pH 5.4, the PCl/PNa was 33 (range of 27-41), similar to that of the wild type, but at pH 7.2, where the histidine should be largely uncharged, PCl/PNa was 3 (range of 2.9-3.1). For the R352C and R352Q mutants, PCl/PNa was 7 (range of 6-8) and 4 (range of 3.5-4.4), respectively. Furthermore, Na+ which does not carry a significant fraction of the current through the wild type is measurably conducted through R352Q. Thus, the charge of the side chain at position 352 is a strong determinant of charge selectivity. In the wild type, the positive charge on Arg352 contributes to an electrostatic potential in the channel that forms a barrier to cation permeation. Mutation of Arg352 did not alter the halide selectivity sequence. Selectivity among halides must involve other residues.
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No. Sentence Comment
101 In cell-attached patches, with 140 mM NaCl in the pipet, the single-channel conductances (in picosiemens) were 6.0 ( 0.3 for the wild type (n ) 7), 5.3 ( 0.3 for R352C (n ) 11), 4.2 ( 0.1 for R352Q (n ) 10), 4.0 ( 0.2 for R352H (n ) 4), and 5.7 ( 0.2 for Q353C (n ) 8).
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ABCC7 p.Arg352His 10220340:101:222
status: NEW114 For the R352H mutant, the single-channel conductance was sensitive to the pH of the bath solution; the single-channel conductance at pH 7.2 was 3.7 ( 0.1 pS (n ) 6), and at pH 5.4, it was 4.3 ( 0.1 pS (n ) 5) (Figure 4).
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ABCC7 p.Arg352His 10220340:114:8
status: NEW131 (B) Average single-channel current-voltage relationships for the wild type (O) and the R352C (0), R352Q (3), and R352H (bath pH of 7.2) (]) mutants.
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ABCC7 p.Arg352His 10220340:131:113
status: NEW133 The symbols for R352Q and R352H overlap at several voltages.
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ABCC7 p.Arg352His 10220340:133:26
status: NEW136 (C and D) Single-channel recordings from inside-out patches obtained from cells expressing either (C) wild-type CFTR or (D) the R352H mutant (bath pH of 7.2).
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ABCC7 p.Arg352His 10220340:136:128
status: NEW149 FIGURE 4: Reversal potential of the R352H mutant which is shifted by the protonation state of the histidine.
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ABCC7 p.Arg352His 10220340:149:36
status: NEW150 Single-channel recordings for R352H at various applied voltages in a 10-fold NaCl gradient as described in Figure 3A except the bath pH was 5.4 (A) and 7.2 (B).
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ABCC7 p.Arg352His 10220340:150:30
status: NEW151 (C) Single-channel current-voltage relationships for R352H with the bath pH at pH 5.4 (O) and pH 7.2 (4).
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ABCC7 p.Arg352His 10220340:151:53
status: NEW158 To determine the role of the positive charge at position 352, we substituted histidine for Arg352.
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ABCC7 p.Arg352His 10220340:158:77
status: NEW160 Maintaining the positive charge at position 352 with the R352H mutation and a bath pH of 5.4 gave a reversal potential Erev of -50.4 ( 1.2 mV (n ) 7) (Figure 4), which was not significantly different from that of the wild type.
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ABCC7 p.Arg352His 10220340:160:57
status: NEW164 These uncharged substitutions also shifted the reversal potential by an amount comparable to that observed by deprotonating R352H; Erev ) -34.9 ( 2 mV (n ) 7) for R352C, and Erev ) -26.3 ( 1.9 mV (n ) 9) for R352Q (Figure 6), resulting in calculated PCl/PNa ratios of 7 (range of 6-8) and 4 (range of 3.5-4.4), respectively.
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ABCC7 p.Arg352His 10220340:164:124
status: NEW221 In the R352H mutant, at a cytoplasmic pH of 5.4 when the histidine is mostly protonated, PCl/PNa ) 33, similar to that of the wild type.
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ABCC7 p.Arg352His 10220340:221:7
status: NEW240 Thus, for the R352H mutant, we infer that the effect of the change in cytoplasmic pH on the Cl- to Na+ permeability ratio is due to a change in the protonation state of the histidine at position 352.5 Similarly, eliminating the positive charge at position 352 by substituting the uncharged amino acids, cysteine or glutamine, reduced PCl/PNa to about 5 (Figure 6).
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ABCC7 p.Arg352His 10220340:240:14
status: NEW278 In contrast, in the R352H mutant raising the pH, presumably deprotonating His352, caused a 10-fold reduction in the Cl- to Na+ permeability ratio.
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ABCC7 p.Arg352His 10220340:278:20
status: NEW279 The fact that substituting other uncharged residues, glutamine and cysteine, at position 352 caused similar changes in the Cl- to Na+ permeability ratio supports our inference that raising the bath pH reduces the charge selectivity of R352H by deprotonation of the histidine at position 352. ability sequence.
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ABCC7 p.Arg352His 10220340:279:235
status: NEW[hide] CFTR: covalent and noncovalent modification sugges... J Gen Physiol. 2001 Oct;118(4):407-31. Smith SS, Liu X, Zhang ZR, Sun F, Kriewall TE, McCarty NA, Dawson DC
CFTR: covalent and noncovalent modification suggests a role for fixed charges in anion conduction.
J Gen Physiol. 2001 Oct;118(4):407-31., [PMID:11585852]
Abstract [show]
The goal of the experiments described here was to explore the possible role of fixed charges in determining the conduction properties of CFTR. We focused on transmembrane segment 6 (TM6) which contains four basic residues (R334, K335, R347, and R352) that would be predicted, on the basis of their positions in the primary structure, to span TM6 from near the extracellular (R334, K335) to near the intracellular (R347, R352) end. Cysteines substituted at positions 334 and 335 were readily accessible to thiol reagents, whereas those at positions 347 and 352 were either not accessible or lacked significant functional consequences when modified. The charge at positions 334 and 335 was an important determinant of CFTR channel function. Charge changes at position 334--brought about by covalent modification of engineered cysteine residues, pH titration of cysteine and histidine residues, and amino acid substitution--produced similar effects on macroscopic conductance and the shape of the I-V plot. The effect of charge changes at position 334 on conduction properties could be described by electrodiffusion or rate-theory models in which the charge on this residue lies in an external vestibule of the pore where it functions to increase the concentration of Cl adjacent to the rate-limiting portion of the conduction path. Covalent modification of R334C CFTR increased single-channel conductance determined in detached patches, but did not alter open probability. The results are consistent with the hypothesis that in wild-type CFTR, R334 occupies a position where its charge can influence the distribution of anions near the mouth of the pore.
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No. Sentence Comment
148 Changes of this magnitude are also seen in oocytes expressing R352Q or R352H CFTR, but were not seen in oocytes expressing wt CFTR.
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ABCC7 p.Arg352His 11585852:148:71
status: NEW154 Importantly, we also obtained a transient response to the application of MTSEA in oocytes expressing R352Q CFTR (Fig. 5 C) or R352H CFTR (unpublished data).
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ABCC7 p.Arg352His 11585852:154:126
status: NEW[hide] Cystic fibrosis transmembrane conductance regulato... Biochemistry. 2009 Oct 27;48(42):10078-88. Alexander C, Ivetac A, Liu X, Norimatsu Y, Serrano JR, Landstrom A, Sansom M, Dawson DC
Cystic fibrosis transmembrane conductance regulator: using differential reactivity toward channel-permeant and channel-impermeant thiol-reactive probes to test a molecular model for the pore.
Biochemistry. 2009 Oct 27;48(42):10078-88., 2009-10-27 [PMID:19754156]
Abstract [show]
The sixth transmembrane segment (TM6) of the CFTR chloride channel has been intensively investigated. The effects of amino acid substitutions and chemical modification of engineered cysteines (cysteine scanning) on channel properties strongly suggest that TM6 is a key component of the anion-conducting pore, but previous cysteine-scanning studies of TM6 have produced conflicting results. Our aim was to resolve these conflicts by combining a screening strategy based on multiple, thiol-directed probes with molecular modeling of the pore. CFTR constructs were screened for reactivity toward both channel-permeant and channel-impermeant thiol-directed reagents, and patterns of reactivity in TM6 were mapped onto two new, molecular models of the CFTR pore: one based on homology modeling using Sav1866 as the template and a second derived from the first by molecular dynamics simulation. Comparison of the pattern of cysteine reactivity with model predictions suggests that nonreactive sites are those where the TM6 side chains are occluded by other TMs. Reactive sites, in contrast, are generally situated such that the respective amino acid side chains either project into the predicted pore or lie within a predicted extracellular loop. Sites where engineered cysteines react with both channel-permeant and channel-impermeant probes occupy the outermost extent of TM6 or the predicted TM5-6 loop. Sites where cysteine reactivity is limited to channel-permeant probes occupy more cytoplasmic locations. The results provide an initial validation of two, new molecular models for CFTR and suggest that molecular dynamics simulation will be a useful tool for unraveling the structural basis of anion conduction by CFTR.
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No. Sentence Comment
182 In those experiments, however, qualitatively identical, reversible reactivity toward MTSEAþ was also seen using either R352Q/wt or R352H/wt CFTR constructs, suggesting that the target of MTSEAþ was 1 of the 18 endogenous cysteines in the R352C/wt protein (7).
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ABCC7 p.Arg352His 19754156:182:136
status: NEW