ABCMdb

ABCC7 p.Tyr109Cys

ClinVar:	c.327T>A , p.Tyr109* ? , not provided c.325T>A , p.Tyr109Asn ? , not provided c.326A>G , p.Tyr109Cys D , Pathogenic
CF databases:	c.325T>A , p.Tyr109Asn (CFTR1) D , The patient is a 51 yearold man from USA, first diagnosed as having cystic fibrosis at the age of 42 years. He had at that time had frequent nasal polyposis episodes and mild pulmonary symptoms. His sputum cultures have repeatedly grown Staphylococcus aereus and once Pseudomonas aaeruginosa. He is not chronically colonised with pseudomonas. He is pancreatic sufficient. His sweat chloride concentration value was 92 mEq/L. [delta]F508 was found on the other allele. c.325T>C , p.Tyr109His (CFTR1) ? , Alonso MJ; Izquierdo I; c.326A>G , p.Tyr109Cys (CFTR1) ? , This mutation is exon 4 of the CFTR gene was found in a patient with CF: A->G at position 458 converting tyrosine 109 to cysteine. It has not been found on other CF- and non CF-chromosomes, minimizing the possibility of a polymorphism. The patinet has an unknown mutation on the other chromosome.
Predicted by SNAP2:	A: D (91%), C: D (63%), D: D (95%), E: D (95%), F: D (63%), G: D (95%), H: D (95%), I: D (91%), K: D (95%), L: D (85%), M: D (95%), N: D (95%), P: D (95%), Q: D (91%), R: D (95%), S: D (95%), T: D (95%), V: D (91%), W: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: N, G: D, H: D, I: N, K: D, L: N, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: N, W: D,

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[hide] Disease-associated mutations in the extracytoplasm... J Biol Chem. 2001 May 4;276(18):14848-54. Epub 2001 Feb 6. Hammerle MM, Aleksandrov AA, Riordan JR
Disease-associated mutations in the extracytoplasmic loops of cystic fibrosis transmembrane conductance regulator do not impede biosynthetic processing but impair chloride channel stability.
J Biol Chem. 2001 May 4;276(18):14848-54. Epub 2001 Feb 6., 2001-05-04 [PMID:11278813]

Abstract [show]
Consistent with its function as a chloride channel regulated entirely from the cytoplasmic side of the plasma membrane, the cystic fibrosis transmembrane conductance regulator (CFTR) glycoprotein exposes little of its mass on the exterior surface of cells. The first and fourth extracytoplasmic loops (ELs) contain approximately 15 and 30 residues, respectively; the other four ELs are extremely short. To examine the influence of missense mutants in ELs detected in patients with cystic fibrosis, we have expressed them in mammalian (baby hamster kidney (BHK21)) cells and assessed their biosynthetic processing and chloride channel activity. In contrast to previous findings that 18 of 30 disease-associated missense mutations in cytoplasmic loops caused retention of the nascent polypeptides in the endoplasmic reticulum, all the EL mutants studied matured and were transported to the cell surface. This pronounced asymmetry is consistent with the notion that endoplasmic reticulum quality control of nascent CFTR is exerted primarily on the cytoplasmic side of the membrane. Although this set of EL mutations has little effect on CFTR maturation, most of them seriously compromise its chloride channel activity. Substitutions at six different positions in EL1 and single positions in EL2 and EL4 all destabilized the open state, some of them severely, indicating that the ELs contribute to the stability of the CFTR ion pore.

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75 TABLE I Oligonucleotide primers used to generate mutations Mutation Primer S108F GGAAGAATCATAGCTTtCTATGACCCGGATAAC Y109C AGAATCATAGCTTCCTgTGACCCGGATAACAAG D110H ATCATAGCTTCCTATcACCCGGATAACAAGGAG P111A ATAGCTTCCTATGACgCGGATAACAAGGAGGAA P111L ATAGCTTCCTATGACCtGGATAACAAGGAGGAA E116K CCGGATAACAAGGAGaAACGCTCTATCGCGATT R117C GATAACAAGGAGGAAtGCTCTATCGCGATTTAT R117H GATAACAAGGAGGAACaCTCTATCGCGATTTAT R117L GATAACAAGGAGGAACtCTCTATCGCGATTTAT R117P GATAACAAGGAGGAACcCTCTATCGCGATTTAT E217G ATGGGGCTAATCTGGGgGTTGTTACAGGCGTCT T908N TATGCAGTGATTATCAaCAGCACCAGTTCGTAT P1013L GTCGCAGTTTTACAACtCTACATCTTTGTTGCA FIG. 2. Login to comment
117 A, squares, wild type; circles, S108F; triangles, Y109C; diamonds, D110H; crosses, wild type without stimulation. Login to comment
122 The substitution of the aromatic tyrosine in the adjacent position by the small thiol residue (Y109C) also results in a very unstable open state, but the tracing is different from that of S108F. Login to comment
171 For example a nucleotide binding domain mutation, G551D, precludes virtually all TABLE II Relative charge transport capacity of mutants Mutants S108F Y109C D110H P111L P111A E116K R117H R117C R117L R117P E217G T908N P1013L Imutant/Iwt 100% 11 15 27 173 105 12 80 27 5 11 10 48 170 FIG. 5. Login to comment

[hide] Predictors of deterioration of lung function in cy... Pediatr Pulmonol. 2002 Jun;33(6):483-91. Schaedel C, de Monestrol I, Hjelte L, Johannesson M, Kornfalt R, Lindblad A, Strandvik B, Wahlgren L, Holmberg L
Predictors of deterioration of lung function in cystic fibrosis.
Pediatr Pulmonol. 2002 Jun;33(6):483-91., [PMID:12001283]

Abstract [show]
The severity of lung disease in cystic fibrosis (CF) may be related to the type of mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and to environmental and immunological factors. Since pulmonary disease is the main determinant of morbidity and mortality in CF, it is important to identify factors that can explain and predict this variation. The aim of this longitudinal study of the whole Swedish CF population over age 7 years was to correlate genetic and clinical data with the rate of decline in pulmonary function. The statistical analysis was performed using the mixed model regression method, supplemented with calculation of relative risks for severe lung disease in age cohorts.The severity of pulmonary disease was to some extent predicted by CFTR genotype. Furthermore, the present investigation is the first long-term study showing a significantly more rapid deterioration of lung function in patients with concomitant diabetes mellitus. Besides diabetes mellitus, pancreatic insufficiency and chronic Pseudomonas colonization were found to be negative predictors of pulmonary function. In contrast to several other reports, we found no significant differences in lung function between genders. Patients with pancreatic sufficiency have no or only a slight decline of lung function with age once treatment is started, but an early diagnosis in this group is desirable.

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121 TABLE 3CFTR Mutations Associated With Pancreatic Sufficiency in Swedish CF Population Y109C S549I/S549I Y109N S945L R117C N1088D À R75Q R117H G1244E L206W 711 þ 3A !G T338I 1249 À 5A !G A455E 2789 þ 5G ! Login to comment

[hide] Cystic fibrosis: a worldwide analysis of CFTR muta... Hum Mutat. 2002 Jun;19(6):575-606. Bobadilla JL, Macek M Jr, Fine JP, Farrell PM
Cystic fibrosis: a worldwide analysis of CFTR mutations--correlation with incidence data and application to screening.
Hum Mutat. 2002 Jun;19(6):575-606., [PMID:12007216]

Abstract [show]
Although there have been numerous reports from around the world of mutations in the gene of chromosome 7 known as CFTR (cystic fibrosis transmembrane conductance regulator), little attention has been given to integrating these mutant alleles into a global understanding of the population molecular genetics associated with cystic fibrosis (CF). We determined the distribution of CFTR mutations in as many regions throughout the world as possible in an effort designed to: 1) increase our understanding of ancestry-genotype relationships, 2) compare mutational arrays with disease incidence, and 3) gain insight for decisions regarding screening program enhancement through CFTR multi-mutational analyses. Information on all mutations that have been published since the identification and cloning of the CFTR gene's most common allele, DeltaF508 (or F508del), was reviewed and integrated into a centralized database. The data were then sorted and regional CFTR arrays were determined using mutations that appeared in a given region with a frequency of 0.5% or greater. Final analyses were based on 72,431 CF chromosomes, using data compiled from over 100 original papers, and over 80 regions from around the world, including all nations where CF has been studied using analytical molecular genetics. Initial results confirmed wide mutational heterogeneity throughout the world; however, characterization of the most common mutations across most populations was possible. We also examined CF incidence, DeltaF508 frequency, and regional mutational heterogeneity in a subset of populations. Data for these analyses were filtered for reliability and methodological strength before being incorporated into the final analysis. Statistical assessment of these variables revealed that there is a significant positive correlation between DeltaF508 frequency and the CF incidence levels of regional populations. Regional analyses were also performed to search for trends in the distribution of CFTR mutations across migrant and related populations; this led to clarification of ancestry-genotype patterns that can be used to design CFTR multi-mutation panels for CF screening programs. From comprehensive assessment of these data, we offer recommendations that multiple CFTR alleles should eventually be included to increase the sensitivity of newborn screening programs employing two-tier testing with trypsinogen and DNA analysis.

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111 Slovakia ∆F508 (57.3%) CFTRdele2,3 (1.2%) 82.7 68.4 14 908/254 CFGAC [1994]; Estivill et al. G542X (6.8%) 3849+10KbC→T (1.0%) [1997]; Dörk et al. [2000]; R553X (4.0%) S42F (0.9%) Macek et al. [2002] N1303K (3.4%) R75X (0.9%) 2143delT (1.8%) G85E (0.9%) R347P (1.4%) 605insT (0.9%) W1282X (1.3%) 1898+1G→A (0.9%) Slovenia ∆F508 (57.8%) R347P (1.1%) 79.7 63.5 16 455/132 CFGAC [1994]; Dörk et al. 2789+5G→A (4.1%) S4X (0.8%) [2000]; Macek et al. [2002] R1162X (3.2%) 457TAT→G (0.8%) G542X (1.9%) D192G (0.8%) Q552X (1.5%) R553X (0.8%) Q685X (1.5%) A559T (0.8%) 3905insT (1.5%) 2907delTT (0.8%) CFTRdele2,3 (1.5%) 3667ins4 (0.8%) Spain ∆F508 (52.7%) G85E (0.8%) 80.2 64.3 21 3608/1356 Chillón et al. [1994]; Casals et G542X (8.0%) R1066C (0.8%) al. [1997]; Estivill et al. [1997] N1303K (2.5%) 2789+5G→A (0.7%) 3601-111G→C (2.0%) 2869insG (0.7%) 1811+1.6Kb A→G (1.7%) ∆I507 (0.6%) R1162X (1.6%) W1282X (0.6%) 711+1G→T (1.3%) L206W (0.5%) R334W (1.2%) R709X (0.5%) Q890X (1.0%) K710X (0.5%) 1609delCA (1.0%) 3272-26A→G (0.5%) 712-1G→T (1.0%) Sweden ∆F508 (66.6%) E60X (0.6%) 85.9 73.8 10 1357/662 Schwartz et al. [1994]; Estivill et 394delTT (7.3%) Y109C (0.6%) al. [1997]; Schaedel et al. 3659delC (5.4%) R117H (0.6%) [1999] 175insT (2.4%) R117C (0.6%) T338I (1.2%) G542X (0.6%) Switzerland ∆F508 (57.2%) K1200E (2.1%) 91.3 83.4 9 1268/1173 Estivill et al. [1997]; R553X (14.0%) N1303K (1.2%) Hergersberg et al. [1997] 3905insT (9.8%) W1282X (1.1%) 1717-1G→A (2.7%) R347P (0.6%) G542X (2.6%) Ukraine ∆F508 (65.2%) CFTRdele2,3 (1.1%) 74.6 55.7 6 1055/580 Estivill et al. [1997]; Dörk et al. R553X (3.6%) G551D (1.8%) [2000]; Macek et al. [2002] N1303K (2.4%) W1282X (0.5%) United ∆F508 (75.3%) 621+1G→T (0.93%) 81.6 66.6 5 19622/9815 Schwartz et al. [1995b]; Kingdom G551D (3.1%) 1717-1G→A (0.57%) Estivill et al. [1997] (total) G542X (1.7%) TABLE 1. Continued. Estimated Projected detection of Number of Number of Country/ allele two CFTR mutations chromosomes Region Mutation array detectiona mutationsb includedc (max/min)d Reference WORLDWIDEANALYSISOFCFTRMUTATIONS585 United ∆F508 (56.6%) 621+1G→T (1.8%) 69.1 47.7 7 456 CFGAC [1994] Kingdom G551D (3.7%) R117H (1.5%) (N. Ireland) R560T (2.6%) ∆I507 (0.9%) G542X (2.0%) United ∆F508 (19.2%) 621+2T→C (3.8%) 84.4 71.2 11 52 Malone et al. [1998] Kingdom Y569D (15.4%) 2184insA (3.8%) (Pakistani) Q98X (11.5%) R560S (1.9%) 1525-1G→A (9.6%) 1898+1G→T (1.9%) 296+12T→C (7.7%) R709X (1.9%) 1161delC (7.7%) United ∆F508 (71.3%) 1717-1G→A (1.0%) 86.4 74.6 9 1236/730 Shrimpton et al. [1991]; Kingdom G551D (5.5%) 621+1G→T (0.6%) Gilfillan et al. [1998] (Scotland) G542X (4.0%) ∆I507 (0.6%) R117H (1.4%) R560T (0.6%) P67L (1.4%) United ∆F508 (71.6%) 1717-1G→A (1.1%) 98.7 97.4 17 183 Cheadle et al. [1993] Kingdom 621+1G→T (6.6%) 3659delC (0.5%) (Wales) 1898+1G→A (5.5%) R117H (0.5%) G542X (2.2%) N1303K (0.5%) G551D (2.2%) E60X (0.5%) 1078delT (2.2%) S549N (0.5%) R1283M (1.6%) 3849+10KbC→T (0.5%) R553X (1.1%) 4016insT (0.5%) ∆I507 (1.1%) Yugoslavia ∆F508 (68.9%) 3849G→A (1.0%) 82.2 67.6 11 709/398 Dabovic et al. [1992]; Estivill et G542X (4.0%) N1303K (0.8%) al. [1997]; Macek et al. R1162C (3.0%) 525delT (0.5%) (submitted for publication) 457TAT→G (1.0%) 621+1G→T (0.5%) I148T (1.0%) G551D (0.5%) Q552X (1.0%) Middle East/Africa Algeria 1) DF508 (20.0%) 4) 1812-1G®A (5.0%) - - 5 20 Loumi et al. [1999] 2) N1303K (20.0%) 5) V754M (5.0%) 3) 711+1G®T (10.0%) Jewish W1282X (48.0%) 3849+10KbC→T (6.0%) 95.0 90.3 6 261 Kerem et al. [1995] (Ashkenazi) ∆F508 (28.0%) N1303K (3.0%) G542X (9.0%) 1717-1G→A (1.0%) Jewish 1) N1303K - - 1 6 Kerem et al. [1995] (Egypt) Jewish 1) Q359K/T360K - - 1 8 Kerem et al. [1995] (Georgia) Jewish 1) DF508 2) 405+1G®A - - 2 11 Kerem et al. [1995] (Libya) Jewish 1) DF508 (72.0%) 3) D1152H (6.0%) - - 3 33 Kerem et al. [1995] (Morocco) 2) S549R (6.0%) Jewish ∆F508 (35.0%) W1282X (2.0%) 43.0 18.5 4 51 Shoshani et al. [1992] (Sepharadim) G542X (4.0%) S549I (2.0%) (Continued) BOBADILLAETAL. Login to comment

[hide] Distribution of CFTR mutations in Saguenay- Lac-Sa... Genet Med. 2008 Mar;10(3):201-6. Madore AM, Prevost C, Dorfman R, Taylor C, Durie P, Zielenski J, Laprise C
Distribution of CFTR mutations in Saguenay- Lac-Saint-Jean: proposal of a panel of mutations for population screening.
Genet Med. 2008 Mar;10(3):201-6., [PMID:18344710]

Abstract [show]
PURPOSE: Saguenay-Lac-Saint-Jean is a region located in the northeastern part of the Province of Quebec, Canada, and is characterized by a founder effect. In this region, it has been documented that the incidence of cystic fibrosis reached 1/902 live births between 1975 and 1988, three times higher than the average incidence of 1/2500 live births reported in other Caucasian populations. This corresponds to a carrier rate of 1/15. METHODS: Using genotyping data from the Canadian Consortium for Cystic Fibrosis Genetic Studies, this article describes the cystic fibrosis transmembrane conductance regulator profile of the cystic fibrosis population living in the Saguenay-Lac-Saint-Jean region and compares it with cystic fibrosis populations living in three other regions of the Province of Quebec. RESULTS: Significant differences in allelic frequencies of common mutations (as DeltaF508, 621 + 1G>T and A455E), and in percentage of covered allele with three or six mutations, were found in Saguenay-Lac-Saint-Jean compared to other regions. Based on this result, two mutation panels exceeding 90% sensitivity threshold are now proposed for cystic fibrosis carrier screening in this region. CONCLUSION: The implementation of the proposed carrier screening program could diminish the incidence of this disease in this region and allow future parents to make informed decisions about family planning.

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48 Altogether, the six mutations represent 95.89% of the CFTR allele of CF patients in the SLSJ population, whereas the proportions are 86.85, 85.27, and Table 2 Cystic fibrosis mutations present in the four populations studied Mutationa Allelic frequency (number of alleles [%]) Populationb 1 2 3 4 „F508 106 (62.35) 55 (72.37) 398 (72.36) 67 (57.78) 621 ؉ 1G>T 42 (24.71) 6 (7.89) 30 (5.45) 1 (0.85) A455E 12 (7.06) 2 (2.63) 14 (2.55) 1 (0.85) 3199del6 1 (0.59) 1 (1.32) 7 (1.27) 1 (0.85) 711 ؉ 1G>T 1 (0.59) 1 (1.32) 15 (2.73) 1 (0.85) Y1092X 1 (0.59) 1 (1.32) 5 (0.91) 0 R117C 2 (1.18) 0 0 0 ‚I507 1 (0.59) 2 (2.63) 10 (1.82) 0 L206W 1 (0.59) 1 (1.32) 9 (1.64) 0 R1158X 1 (0.59) 0 0 0 S489X 1 (0.59) 0 1 (0.18) 0 R553X 0 2 (2.63) 2 (0.36) 0 R334W 0 1 (1.32) 2 (0.36) 0 G542X 0 0 10 (1.82) 0 G85E 0 0 6 (1.09) 5 (4.24) N1303K 0 0 5 (0.91) 1 (0.85) IVS8-5T 0 0 4 (0.73) 0 W1282X 0 0 3 (0.55) 7 (5.93) R347P 0 0 1 (0.18) 2 (1.69) V520F 0 0 1 (0.18) 0 I1027T 0 0 1 (0.18) 0 R1066C/IVS 0 0 1 (0.18) 0 Q1313X 0 0 1 (0.18) 0 1898ϩ3GϾA 0 0 1 (0.18) 0 2183AAϾG 0 0 1 (0.18) 0 2951insA 0 0 1 (0.18) 0 G551D 0 0 0 2 (1.69) 1525-iG-A 0 0 0 2 (1.69) Y109C 0 0 0 1 (0.85) S549N 0 0 0 1 (0.85) 3154del1G 0 0 0 1 (0.85) UNKNOWN 1 (0.59) 4 (5.26) 20 (3.82) 25 (21.19) Number of alleles genotypedc 170 (100) 76 (100) 550 (100) 118 (100) a The six mutations included in the panels proposed are in bold. Login to comment

[hide] A novel cystic fibrosis mutation, Y109C, in the fi... Hum Mol Genet. 1994 Jun;3(6):1001-2. Schaedel C, Kristoffersson AC, Kornfalt R, Holmberg L
A novel cystic fibrosis mutation, Y109C, in the first transmembrane domain of CFTR.
Hum Mol Genet. 1994 Jun;3(6):1001-2., [PMID:7524909]

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1 6 -1002 A novel cystic fibrosis mutation, Y109C, in the first transmembrane domain of CFTR Charlotta Schaedel*, Ann-Charlotte Kristoffersson, Ragnhild Kornfalt and Lars Holmberg Department of Paediatrics, University Hospital, S-221 85 Lund, Sweden Received February 3, 1994; Revised and Accepted March 22, 1994 Cystic fibrosis (CF) is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein, which forms a cAMP-regulated chloride channel. Login to comment
18 An A -G transition was found in exon 4 at nucleotide position 458 converting tyrosine 109 to cysteine (Y109C) (Fig. Login to comment
22 The patient also had a 3659delC mutation in exon 19 like her mother, who lacked Y109C. Login to comment
25 We can thus conclude that among the two mutations detected in our patient Y109C should be the mutation conferring pancreatic sufficiency. Login to comment
26 The Y109C substitution occurs in the first transmembrane domain of CFTR in a 15 amino acid residue sequence that is located between the first and second membrane-spanning segments and predicted to be at the external side of the membrane (9). Login to comment
31 The Y109C substitution does not alter a charge, which suggests that conformational transitions imposed by changes of single structural elements in the 15 residue sequence can have a substantial effect on channel properties. Login to comment
36 At position 458 there is a G in addition to an A convening tyrosine 109 to cysteine in one allele. Login to comment

[hide] Cysteine scanning of CFTR's first transmembrane se... Biophys J. 2013 Feb 19;104(4):786-97. doi: 10.1016/j.bpj.2012.12.048. Gao X, Bai Y, Hwang TC
Cysteine scanning of CFTR's first transmembrane segment reveals its plausible roles in gating and permeation.
Biophys J. 2013 Feb 19;104(4):786-97. doi: 10.1016/j.bpj.2012.12.048., [PMID:23442957]

Abstract [show]
Previous cysteine scanning studies of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel have identified several transmembrane segments (TMs), including TM1, 3, 6, 9, and 12, as structural components of the pore. Some of these TMs such as TM6 and 12 may also be involved in gating conformational changes. However, recent results on TM1 seem puzzling in that the observed reactive pattern was quite different from those seen with TM6 and 12. In addition, whether TM1 also plays a role in gating motions remains largely unknown. Here, we investigated CFTR's TM1 by applying methanethiosulfonate (MTS) reagents from both cytoplasmic and extracellular sides of the membrane. Our experiments identified four positive positions, E92, K95, Q98, and L102, when the negatively charged MTSES was applied from the cytoplasmic side. Intriguingly, these four residues reside in the extracellular half of TM1 in previously defined CFTR topology; we thus extended our scanning to residues located extracellularly to L102. We found that cysteines introduced into positions 106, 107, and 109 indeed react with extracellularly applied MTS probes, but not to intracellularly applied reagents. Interestingly, whole-cell A107C-CFTR currents were very sensitive to changes of bath pH as if the introduced cysteine assumes an altered pKa-like T338C in TM6. These findings lead us to propose a revised topology for CFTR's TM1 that spans at least from E92 to Y109. Additionally, side-dependent modifications of these positions indicate a narrow region (L102-I106) that prevents MTS reagents from penetrating the pore, a picture similar to what has been reported for TM6. Moreover, modifications of K95C, Q98C, and L102C exhibit strong state dependency with negligible modification when the channel is closed, suggesting a significant rearrangement of TM1 during CFTR's gating cycle. The structural implications of these findings are discussed in light of the crystal structures of ABC transporters and homology models of CFTR.

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105 Further addition of a specific CFTR inhibitor, CFTRinh-172 (39,40), caused a minor decrease of the residual current, indicating a drastic reduction of I106C-CFTR currents by external MTSES. Similar results were obtained for A107C- and Y109C-CFTR except that the magnitude of inhibition for A107C-CFTR is significantly smaller (Fig. 3 C). Login to comment

[hide] Three charged amino acids in extracellular loop 1 ... J Gen Physiol. 2014 Aug;144(2):159-79. doi: 10.1085/jgp.201311122. Epub 2014 Jul 14. Cui G, Rahman KS, Infield DT, Kuang C, Prince CZ, McCarty NA
Three charged amino acids in extracellular loop 1 are involved in maintaining the outer pore architecture of CFTR.
J Gen Physiol. 2014 Aug;144(2):159-79. doi: 10.1085/jgp.201311122. Epub 2014 Jul 14., [PMID:25024266]

Abstract [show]
The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) bears six extracellular loops (ECL1-6); ECL1 is the site of several mutations associated with CF. Mutation R117H has been reported to reduce current amplitude, whereas D110H, E116K, and R117C/L/P may impair channel stability. We hypothesized that these amino acids might not be directly involved in ion conduction and permeation but may contribute to stabilizing the outer vestibule architecture in CFTR. We used cRNA injected oocytes combined with electrophysiological techniques to test this hypothesis. Mutants bearing cysteine at these sites were not functionally modified by extracellular MTS reagents and were blocked by GlyH-101 similarly to WT-CFTR. These results suggest that these three residues do not contribute directly to permeation in CFTR. In contrast, mutants D110R-, E116R-, and R117A-CFTR exhibited instability of the open state and significantly shortened burst duration compared with WT-CFTR and failed to be locked into the open state by AMP-PNP (adenosine 5'-(beta,gamma-imido) triphosphate); charge-retaining mutants showed mainly the full open state with comparably longer open burst duration. These interactions suggest that these ECL1 residues might be involved in maintaining the outer pore architecture of CFTR. A CFTR homology model suggested that E116 interacts with R104 in both the closed and open states, D110 interacts with K892 in the fully closed state, and R117 interacts with E1126 in the open state. These interactions were confirmed experimentally. The results suggest that D110, E116, and R117 may contribute to stabilizing the architecture of the outer pore of CFTR by interactions with other charged residues.

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36 CF-causing mutations have been identified in ECL1, including S108F, Y109C/N, D110H/ Y/N,P111A/L,E116K/Q,andR117C/G/H/P/L.Among these residues, D110, E116, and R117 are charged amino acids fully conserved among nine species (Fig. 1 A). Login to comment