ABCC7 p.Thr338Asn
| ClinVar: |
c.1012A>G
,
p.Thr338Ala
?
, not provided
c.1013C>T , p.Thr338Ile D , Pathogenic |
| CF databases: |
c.1013C>T
,
p.Thr338Ile
D
, CF-causing ; CFTR1: A nucleotide change C->T at position 1145 which causes the replacement of a Threonine by Isoleucine residue in codon 338 of exon 7.
c.1012A>G , p.Thr338Ala (CFTR1) ? , This mutation was identified in one Iranian CBAVD patient. |
| Predicted by SNAP2: | A: D (85%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (53%), K: D (95%), L: D (95%), M: D (95%), N: D (91%), P: D (95%), Q: D (95%), R: D (95%), S: D (91%), V: D (85%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: N, C: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: N, P: N, Q: D, R: D, S: N, V: N, W: D, Y: D, |
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[hide] Non-pore lining amino acid side chains influence a... J Physiol. 1998 Oct 1;512 ( Pt 1):1-16. Linsdell P, Zheng SX, Hanrahan JW
Non-pore lining amino acid side chains influence anion selectivity of the human CFTR Cl- channel expressed in mammalian cell lines.
J Physiol. 1998 Oct 1;512 ( Pt 1):1-16., 1998-10-01 [PMID:9729613]
Abstract [show]
1. The effects of individually mutating two adjacent threonine residues in the sixth membrane-spanning region (TM6) of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel on permeation properties were examined using patch clamp recording from mammalian cell lines stably expressing human CFTR. 2. A number of mutations of T338 significantly affected the permeation properties of the channel. Increases and decreases in single channel conductance were observed for different mutants. Anion selectivity was strongly affected, with no two channel variants sharing the same selectivity sequence. Several mutations led to strong inward rectification of the macroscopic current-voltage relationship. The effects of these mutations on permeation properties were correlated with the size of the amino acid side chain substituted, rather than its chemical nature. 3. Most mutations of T339 resulted in a lack of functional channel expression and apparent misprocessing of the protein. One mutant, T339V, was characterized in detail; its permeation properties were significantly altered, although these effects were not as strong as for T338 mutations. 4. These results suggest an important role for T338 in controlling the permeation properties of the CFTR Cl- channel. It is suggested that mutation of this residue alters the interaction between permeating anions and the channel pore via an indirect effect on the orientation of the TM6 helix.
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None has been submitted yet.
No. Sentence Comment
84 Example macroscopic current-voltage relationships for wild-type and T338 mutant CFTRs, recorded with symmetrical Cl¦-containing solutions Note the inward rectification observed with some T338 mutants, especially T338N.
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ABCC7 p.Thr338Asn 9729613:84:217
status: NEW92 Rectification was particularly strong in T338N (-I+ 50ÏI-50 = 0·33 ± 0·05; n = 6).
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ABCC7 p.Thr338Asn 9729613:92:41
status: NEW94 However, clear single channel currents were never resolved for T338N, T338V or T338I, either in CHO cell patches or in patches excised from BHK cells selected using a lower concentration of MTX (20 ìÒ), at potentials as hyperpolarized as -100 mV (data not shown).
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ABCC7 p.Thr338Asn 9729613:94:63
status: NEW101 We attempted to make some estimate of the conductance of T338N, T338V and T338I channels by analysing the increase in current noise associated with macroscopic current activation (Fig. 5).
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ABCC7 p.Thr338Asn 9729613:101:57
status: NEW111 In contrast to wild-type, activation of macroscopic T338I (Fig. 5C and D) and T338N and T338V (data not shown) Cl¦ currents was associated with only a very small increase in noise.
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ABCC7 p.Thr338Asn 9729613:111:78
status: NEW112 Analysis of current variance (e.g. Fig. 5D) yielded chord conductances at -50 mV of 0·23 ± 0·02 pS (n = 4) for T338N, 0·36 ± 0·10 pS (n = 5) for T338V, and 0·17 ± 0·04 pS (n = 5) for T338I.
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ABCC7 p.Thr338Asn 9729613:112:126
status: NEW142 Permeability of intracellular anions in wild-type and mutant CFTR Cl¦ channels ------------------------------------------------------------ Anion WT T338A T338S T338N T338V T339V ------------------------------------------------------------ Thiocyanate 2·63 ± 0·13 (6) 5·85 ± 0·27 (4)* 4·80 ± 0·19 (3)* 8·72 ± 1·03 (4)* 1·92 ± 0·35 (4)* 3·28 ± 0·08 (4)* Nitrate 1·53 ± 0·04 (7) 2·04 ± 0·08 (3)* 1·82 ± 0·03 (4)* 4·22 ± 0·22 (3)* 6·84 ± 1·18 (7)* 1·61 ± 0·02 (3) Bromide 1·23 ± 0·03 (5) 1·74 ± 0·04 (3)* 1·47 ± 0·07 (3)* 1·66 ± 0·15 (3)* 1·04 ± 0·09 (5) 1·39 ± 0·06 (4)* Chloride 1·00 ± 0·01 (10) 1·00 ± 0·02 (11) 1·00 ± 0·02 (6) 1·00 ± 0·03 (10) 1·00 ± 0·04 (11) 1·00 ± 0·06 (10) Iodide 0·84 ± 0·03 (5) 2·09 ± 0·16 (5)* 1·76 ± 0·09 (3)* 1·03 ± 0·05 (3)* 0·79 ± 0·11 (3) 0·84 ± 0·02 (3) Perchlorate 0·25 ± 0·02 (6) 1·35 ± 0·08 (3)* 0·66 ± 0·06 (3)* 0·41 ± 0·03 (3)* 0·54 ± 0·00 (3)* 0·24 ± 0·01 (4) Benzoate 0·069 ± 0·006 (6) 0·17 ± 0·03 (4)* 0·091 ± 0·019 (3) 0·089 ± 0·015 (4) 0·15 ± 0·02 (4)* 0·097 ± 0·014 (4) Hexafluorophosphate < 0·019 (4) 0·53 ± 0·01 (3)* 0·31 ± 0·02 (3)* 0·68 ± 0·02 (3)* 0·39 ± 0·05 (3)* 0·051 ± 0·010 (4)* Fluoride 0·11 ± 0·01 (7) 0·12 ± 0·02 (4) 0·095 ± 0·012 (4) 0·11 ± 0·01 (4) 0·093 ± 0·009 (3) 0·17 ± 0·02 (4)* Formate 0·25 ± 0·01 (8) 0·45 ± 0·04 (3)* 0·43 ± 0·03 (3)* 0·35 ± 0·04 (4)* 0·22 ± 0·01 (3) 0·28 ± 0·02 (3) Acetate 0·090 ± 0·004 (8) 0·19 ± 0·01 (3)* 0·18 ± 0·01 (3)* 0·10 ± 0·02 (5) 0·11 ± 0·02 (3) 0·16 ± 0·01 (3)* Propanoate 0·14 ± 0·01 (3) 0·18 ± 0·02 (4) 0·098 ± 0·010 (4)* 0·077 ± 0·013 (3)* 0·13 ± 0·02 (3) - Pyruvate 0·10 ± 0·01 (5) 0·20 ± 0·01 (3)* 0·13 ± 0·02 (3) 0·075 ± 0·015 (3) 0·17 ± 0·03 (3)* - Methane sulphonate 0·077 ± 0·005 (5) 0·14 ± 0·02 (4)* 0·079 ± 0·014 (3) 0·038 ± 0·004 (3)* 0·088 ± 0·007 (3) - Glutamate 0·096 ± 0·008 (4) 0·082 ± 0·009 (3) 0·080 ± 0·008 (3) 0·060 ± 0·012 (5)* 0·11 ± 0·01 (3) - Isethionate 0·13 ± 0·01 (4) 0·11 ± 0·01 (3) 0·086 ± 0·012 (5)* 0·043 ± 0·007 (3)* 0·067 ± 0·005 (3)* - Gluconate 0·068 ± 0·004 (36) 0·10 ± 0·01 (3)* 0·060 ± 0·004 (3) 0·044 ± 0·004 (3) 0·077 ± 0·009 (3) 0·088 ± 0·021 (5) ------------------------------------------------------------ Relative permeabilities of different anions present in the intracellular solution under biionic conditions were calculated from macroscopic current reversal potentials (e.g. Figs 7 and 10) as described in Methods.
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ABCC7 p.Thr338Asn 9729613:142:166
status: NEW151 However, the permeabilities of the low conductance mutants T338N and T338V were more difficult to interpret, possibly indicating that substitution of a larger amino acid for T338 causes a more severe disruption of pore function.
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ABCC7 p.Thr338Asn 9729613:151:59
status: NEW153 Pore diameter of T338 mutants Previously, we suggested that the double mutant channel, TT338,339AA, had an increased minimum functional pore diameter, based on its increased permeability to extracellular formate, acetate, propanoate and pyruvate ions (Linsdell et P. Linsdell, S.-X. Zheng and J. W. Hanrahan J. Physiol. 512.18 -------------------------------------------------------------------------------------------- Table 2 ---------------------------------------------- Wild-type SCN¦ > NOצ > Br¦ > Cl¦ > I¦ > ClOÚ¦ > formate > F¦ > PFܦ T338A SCN¦ > I¦ ü NOצ > Br¦ > ClOÚ¦ > Cl¦ > PFܦ > formate > F¦ T338S SCN¦ > NOצ ü I¦ > Br¦ > Cl¦ > ClOÚ¦ > formate > PFܦ > F¦ T338N SCN¦ > NOצ > Br¦ > I¦ = Cl¦ > PFܦ > ClOÚ¦ > formate > F¦ T338V NOצ > SCN¦ > Br¦ = Cl¦ > I¦ > ClOÚ¦ > PFܦ > formate > F¦ -------------------------------------------------------------------------------------------- Figure 7.
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ABCC7 p.Thr338Asn 9729613:153:849
status: NEW164 In each case the data have been fitted by eqn (2), giving minimum functional pore diameters of 0·528 nm (wild-type), 0·576 nm (T338A), 0·549 nm (T338S), 0·510 nm (T338N) and 0·540 nm (T338V).
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ABCC7 p.Thr338Asn 9729613:164:183
status: NEW168 In each case the data have been fitted using eqn (2) (see Methods), giving estimates of the functional pore diameter (d) of 0·528 nm for wild-type, 0·576 nm for T338A, 0·549 nm for T338S, 0·510 nm for T338N and 0·540 nm for T338V. Anions examined (in order of increasing diameter) were: SCN¦, Cl¦, NOצ, Br¦, I¦, ClOÚ¦, benzoate and PFܦ.
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ABCC7 p.Thr338Asn 9729613:168:221
status: NEW171 In this case, fits by eqn (2) suggested minimum pore diameters of 0·535 nm (wild-type), 0·615 nm (T338A), 0·505 nm (T338S), 0·503 nm (T338N) and 0·530 nm (T338V).
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ABCC7 p.Thr338Asn 9729613:171:154
status: NEW181 In each case the data have been fitted using eqn (2) (see Methods), giving estimates of the functional pore diameter (d) of 0·535 nm for wild type, 0·615 nm for T338A, 0·505 nm for T338S, 0·503 nm for T338N and 0·530 nm for T338V. Anions examined (in order of increasing diameter) were: formate, acetate, propanoate, pyruvate, methane sulphonate and gluconate.)
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ABCC7 p.Thr338Asn 9729613:181:221
status: NEW193 The conductance of different T338 mutants varied over almost two orders of magnitude (Fig. 6), although the low conductances estimated for T338N, T338V and T338I should be considered rough approximations only.
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ABCC7 p.Thr338Asn 9729613:193:139
status: NEW207 All single channel conductances reported in this paper were measured at hyperpolarized potentials; conductance of the mutant channels T338N, T338V and T338I might be significantly lower at depolarized potentials (Fig. 2).
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ABCC7 p.Thr338Asn 9729613:207:134
status: NEW