ABCMdb

PMID: 9379167

Tabcharani JA, Linsdell P, Hanrahan JW
Halide permeation in wild-type and mutant cystic fibrosis transmembrane conductance regulator chloride channels.
J Gen Physiol. 1997 Oct;110(4):341-54., [PubMed]

Sentences

No. Mutations Sentence Comment

12 ABCC7 p.Arg347Asp The switch to low I- permeability was enhanced at potentials that favored Cl- entry into the pore and was not observed in the R347D mutant, which is thought to lack an anion binding site involved in multi-ion pore behavior. Login to comment 15 ABCC7 p.Arg347Asp The switch to low I2 permeability was enhanced at potentials that favored Cl2 entry into the pore and was not observed in the R347D mutant, which is thought to lack an anion binding site involved in multi-ion pore behavior. Login to comment 21 ABCC7 p.Gly551Asp ABCC7 p.Arg117His ABCC7 p.Ala455Glu ABCC7 p.Arg347Pro Mutations in CFTR that cause it to be mislocalized (i.e., ⌬F508) or unresponsive (i.e., G551D) are associated with severe forms of cystic fibrosis, whereas mutations that only partially reduce CFTR conductance (R347P,H, Sheppard et al., 1993; Tabcharani et al., 1993), open probability (R117H, Sheppard et al., 1993; Becq et al., 1994; intracellular loop IV mutants, Seibert et al., 1996), or processing (A455E, Sheppard et al., 1995) are associated with milder symptoms. Login to comment 24 ABCC7 p.Gly551Asp ABCC7 p.Arg117His ABCC7 p.Ala455Glu ABCC7 p.Arg347Pro Mutations in CFTR that cause it to be mislocalized (i.e., DF508) or unresponsive (i.e., G551D) are associated with severe forms of cystic fibrosis, whereas mutations that only partially reduce CFTR conductance (R347P,H, Sheppard et al., 1993; Tabcharani et al., 1993), open probability (R117H, Sheppard et al., 1993; Becq et al., 1994; intracellular loop IV mutants, Seibert et al., 1996), or processing (A455E, Sheppard et al., 1995) are associated with milder symptoms. Login to comment 33 ABCC7 p.Arg347Asp This switch to low I- permeability was accelerated by holding the membrane at potentials that favored Cl- entry into the channel, and was not observed in R347D CFTR, a mutant shown previously to lack multi-ion pore behavior in mixtures of Cl- and thiocyanate. Login to comment 35 ABCC7 p.Arg347Asp ABCC7 p.Arg347Asp m e t h o d s Cells Chinese hamster ovary (CHO) cells expressing wild-type CFTR or the mutant R347D (arginine 347 in the sixth predicted membrane spanning region mutated to aspartate) have been described previously (Tabcharani et al., 1991; Chang et al., 1993; Tabcharani et al., 1993). Login to comment 37 ABCC7 p.Arg347Asp m e t h o d s Cells Chinese hamster ovary (CHO) cells expressing wild-type CFTR or the mutant R347D (arginine 347 in the sixth predicted membrane spanning region mutated to aspartate) have been described previously (Tabcharani et al., 1991; Chang et al., 1993; Tabcharani et al., 1993). Login to comment 169 ABCC7 p.Arg347Asp To assess the possible role of this residue in I- permeation and block, we studied the I- selectivity of a mutant in which this residue was converted to aspartate (R347D). Login to comment 173 ABCC7 p.Arg347Asp Most significantly, the permeability ratio PI/PCl was not protocol dependent in the R347D mutant. Login to comment 174 ABCC7 p.Arg347Asp Iodide currents through R347D could be measured indefinitely after Cl- cur- rents had been allowed to flow for several minutes. Login to comment 175 ABCC7 p.Arg347Asp The inability of R347D to distinguish between I- and Cl- ions suggests arg347 may contribute to the selectivity filter. Login to comment 179 ABCC7 p.Arg347Asp To assess the possible role of this residue in I2 permeation and block, we studied the I2 selectivity of a mutant in which this residue was converted to aspartate (R347D). Login to comment 184 ABCC7 p.Arg347Asp Most significantly, the permeability ratio PI/PCl was not protocol dependent in the R347D mutant. Login to comment 185 ABCC7 p.Arg347Asp Iodide currents through R347D could be measured indefinitely after Cl2 currents had been allowed to flow for several minutes. Login to comment 186 ABCC7 p.Arg347Asp The inability of R347D to distinguish between I2 and Cl2 ions suggests arg347 may contribute to the selectivity filter. Login to comment 214 ABCC7 p.Arg347Glu ABCC7 p.Arg347Asp In this regard, the mutant R347D had normal anion:cation permeability ratios (Linsdell and Hanrahan, unpublished observations) as did R347E (Anderson et al., 1991), but arg352, which has also been proposed to form part of the anion selectivity filter, remains a candidate. Login to comment 231 ABCC7 p.Arg347Glu ABCC7 p.Arg347Asp In this regard, the mutant R347D had normal anion:cation permeability ratios (Linsdell and Hanrahan, unpublished observations) as did R347E (Anderson et al., 1991), but arg352, which has also been proposed to form part of the anion selectivity filter, remains a candidate. Login to comment 232 ABCC7 p.Arg347Asp Selectivity of the CFTR channel mutant R347D. Login to comment 234 ABCC7 p.Arg347Asp (B) Mean current-voltage relationships obtained when patches containing the R347D mutant are bathed externally with NaCl solution and internally with (᭹) NaCl or (᭺) NaI solution. Login to comment 236 ABCC7 p.Arg347Asp Cl- conductance of the R347D mutant was reduced by almost half in symmetrical Cl solution, as reported previously (Tabcharani et al., 1993). Login to comment 249 ABCC7 p.Arg347Asp Selectivity of the CFTR channel mutant R347D. Login to comment 251 ABCC7 p.Arg347Asp (B) Mean current-voltage relationships obtained when patches containing the R347D mutant are bathed externally with NaCl solution and internally with (d) NaCl or (s) NaI solution. Login to comment 253 ABCC7 p.Arg347Asp Cl2 conductance of the R347D mutant was reduced by almost half in symmetrical Cl solution, as reported previously (Tabcharani et al., 1993). Login to comment 264 ABCC7 p.Arg347Glu ABCC7 p.Lys335Glu ABCC7 p.Lys95Glu ABCC7 p.Arg1030Glu Arg347 May Contribute to a Weak Field Strength Site for Iodide High macroscopic PI/PCl ratios have been reported previously for CFTR channels in which positively charged residues in the membrane spanning regions were mutated to negatively charged residues (K95E, 1.43; K335E, 1.37; R347E, 0.9; R1030E, 0.81; Anderson et al., 1991). Login to comment 265 ABCC7 p.Arg347Glu ABCC7 p.Arg347Asp The PI/PCl ratio obtained for R347D under biionic conditions is intermediate between Iunbl and Ibl in the wild-type channel, and is consistent with the value of 0.9 reported previously for R347E (Anderson et al., 1991). Login to comment 277 ABCC7 p.Arg347Asp ABCC7 p.Lys335Glu ABCC7 p.Lys95Asp Halide selectivity in CFTR cannot be attributed exclusively to the region around arg347; however, because high PI/PCl ratios have been reported previously for other pore mutants (K95D and K335E; Anderson et al., 1991), and because R347D retains some preference for Br- over Cl- and selects strongly against F- (our unpublished observations). Login to comment 278 ABCC7 p.Arg347Asp ABCC7 p.Lys335Glu PI/PCl was altered by a mutation that abolished the anomalous mole fraction effect (AMFE, R347D); however, these properties are not strictly correlated because K335E also had high PI/PCl in a previous study (Anderson et al., 1991) and yet displays an AMFE in SCN--Cl- mixtures (Tabcharani et al., 1993). Login to comment 289 ABCC7 p.Arg347Glu ABCC7 p.Lys335Glu ABCC7 p.Lys95Glu ABCC7 p.Arg1030Glu Arg347 May Contribute to a Weak Field Strength Site for Iodide High macroscopic PI/PCl ratios have been reported previously for CFTR channels in which positively charged residues in the membrane spanning regions were mutated to negatively charged residues (K95E, 1.43; K335E, 1.37; R347E, 0.9; R1030E, 0.81; Anderson et al., 1991). Login to comment 290 ABCC7 p.Arg347Glu ABCC7 p.Arg347Asp The PI/PCl ratio obtained for R347D under biionic conditions is intermediate between Iunbl and Ibl in the wild-type channel, and is consistent with the value of 0.9 reported previously for R347E (Anderson et al., 1991). Login to comment 305 ABCC7 p.Arg347Asp ABCC7 p.Lys335Glu ABCC7 p.Lys95Asp Halide selectivity in CFTR cannot be attributed exclusively to the region around arg347; however, because high PI/PCl ratios have been reported previously for other pore mutants (K95D and K335E; Anderson et al., 1991), and because R347D retains some preference for Br2 over Cl2 and selects strongly against F2 (our unpublished observations). Login to comment 306 ABCC7 p.Arg347Asp ABCC7 p.Lys335Glu PI/PCl was altered by a mutation that abolished the anomalous mole fraction effect (AMFE, R347D); however, these properties are not strictly correlated because K335E also had high PI/PCl in a previous study (Anderson et al., 1991) and yet displays an AMFE in SCN2-Cl2 mixtures (Tabcharani et al., 1993). Login to comment