ABCMdb

ABCC7 p.Gly1069Cys

ClinVar:	c.3205G>A , p.Gly1069Arg ? , not provided
CF databases:	c.3205G>A , p.Gly1069Arg ? , Varying clinical consequence ; CFTR1: This mutation was identified in a Bulgarian patient in collaboration with Dr. Kalaydjieva et al.
Predicted by SNAP2:	A: N (72%), C: N (66%), D: N (66%), E: N (66%), F: D (75%), H: N (82%), I: D (71%), K: N (93%), L: N (53%), M: D (66%), N: N (87%), P: D (53%), Q: N (82%), R: N (72%), S: N (87%), T: N (66%), V: D (66%), W: D (71%), Y: D (75%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, H: N, I: D, K: N, L: D, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: D, W: D, Y: D,

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Publications
[hide] Phenylalanine-508 mediates a cytoplasmic-membrane ... Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3256-61. Epub 2008 Feb 27. Serohijos AW, Hegedus T, Aleksandrov AA, He L, Cui L, Dokholyan NV, Riordan JR
Phenylalanine-508 mediates a cytoplasmic-membrane domain contact in the CFTR 3D structure crucial to assembly and channel function.
Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3256-61. Epub 2008 Feb 27., 2008-03-04 [PMID:18305154]

Abstract [show]
Deletion of phenylalanine-508 (Phe-508) from the N-terminal nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP-binding cassette (ABC) transporter family, disrupts both its folding and function and causes most cystic fibrosis. Most mutant nascent chains do not pass quality control in the ER, and those that do remain thermally unstable, only partially functional, and are rapidly endocytosed and degraded. Although the lack of the Phe-508 peptide backbone diminishes the NBD1 folding yield, the absence of the aromatic side chain is primarily responsible for defective CFTR assembly and channel gating. However, the site of interdomain contact by the side chain is unknown as is the high-resolution 3D structure of the complete protein. Here we present a 3D structure of CFTR, constructed by molecular modeling and supported biochemically, in which Phe-508 mediates a tertiary interaction between the surface of NBD1 and a cytoplasmic loop (CL4) in the C-terminal membrane-spanning domain (MSD2). This crucial cytoplasmic membrane interface, which is dynamically involved in regulation of channel gating, explains the known sensitivity of CFTR assembly to many disease-associated mutations in CL4 as well as NBD1 and provides a sharply focused target for small molecules to treat CF. In addition to identifying a key intramolecular site to be repaired therapeutically, our findings advance understanding of CFTR structure and function and provide a platform for focused biochemical studies of other features of this unique ABC ion channel.

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No. Sentence Comment
71 Cross-linking of Cys pairs F508C/L1065C, F508C/F1068C, F508C/G1069C, and F508C/F1074C confirms that Phe-508 in NBD1 associates with CL4 in MSD2 (Fig. 3 and SI Fig. 7). Login to comment
80 Cross-linking also occurs between cysteines substituted for another hydrophobic residue (Val-510) near Phe-508 on the NBD1 surface and G1069C in CL4 (SI Fig. 8). Login to comment
81 In addition to the Phe-508-containing NBD1 surface patch, residues in other regions of the domain also interact with CL4 residues as evidenced by cross-linking of Cys pairs involving amino acids closer to the Q loop (Gln-493), including W496C/T1064C and M498C/L1065C as well as nearer the Walker B motif (Asp-572) such as K564C/G1069C (Fig. 3A and SI Fig. 8). Login to comment
84 Nevertheless, the proximity or relative orientation of the F508C/F1068C, F508C/G1069C, and V510C/G1069C pairs permitted very little disulfide bond formation on oxidation catalyzed by copper phenanthroline, i.e., only a very small proportion of mature band was converted to cross-linked band Fig. 2. Login to comment
97 Phe-508 participates in an apparent aromatic cluster with residues from CL4(seealsoSIFig.10).CL4alsointeractswithotherregionsinNBD1assuggested by cross-linking of residues close to the Q loop (W496C/T1064C and M498C/ L1065C) and a residue near the Walker B motif (K564C/G1069C). Login to comment

[hide] Restoration of domain folding and interdomain asse... FASEB J. 2010 Aug;24(8):3103-12. Epub 2010 Mar 16. He L, Aleksandrov LA, Cui L, Jensen TJ, Nesbitt KL, Riordan JR
Restoration of domain folding and interdomain assembly by second-site suppressors of the DeltaF508 mutation in CFTR.
FASEB J. 2010 Aug;24(8):3103-12. Epub 2010 Mar 16., [PMID:20233947]

Abstract [show]
Deletion of PHE508 (DeltaF508) from the first nucleotide-binding domain (NBD1) of CFTR, which causes most cystic fibrosis, disrupts the folding and assembly of the protein. Although the folding pathways and yield of isolated NBD1 are altered, its global structure is not, and details of the changes in the rest of the protein remain unclear. To gain further insight into how the whole mutant protein is altered, we have determined the influence of known second-site suppressor mutations in NBD1 on the conformation of this domain and key interfaces between domains. We found that the suppressors restored maturation of only those processing mutations located in NBD1, but not in other domains, including those in the C-terminal cytoplasmic loop of the second membrane-spanning domain, which forms an interface with the NBD1 surface. Nevertheless, the suppressors promoted the formation of this interface and others in the absence of F508. The suppressors restored maturation in a DeltaF508 construct from which NBD2 was absent but to a lesser extent than in the full-length, indicating that DeltaF508 disrupts interactions involving NBD2, as well as other domains. Rescue of DeltaF508-CFTR by suppressors required the biosynthesis of the entire full-length protein in continuity, as it did not occur when N- and C-terminal "halves" were coexpressed. Simultaneous with these interdomain perturbations, DeltaF508 resulted in suppressor reversed alterations in accessibility of residues both in the F508-containing NBD1 surface loop and in the Q loop within the domain core. Thus, in the context of the full-length protein, DeltaF508 mutation causes detectable changes in NBD1 conformation, as well as interdomain interactions.

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123 Cys- pair cross-linking also was not observed with Cys pairs at V510C/G1069C and K564C/G1069C in the NBD1/ CL4 interface of ⌬F508-CFTR (Fig. 3B). Login to comment
126 In addition, Cys pairs V510C/G1069C and K564C/G1069C at the NBD1/CL4 interface also were able to be cross-linked by M3M and M8M (Fig. 3B). Login to comment
205 This may reflect the involvement of this loop in the NBD1/CL4 interface, as shown with the cross-linking of V510C/ G1069C in the mature but not in the immature form (18). Login to comment

[hide] Regulatory insertion removal restores maturation, ... J Mol Biol. 2010 Aug 13;401(2):194-210. Epub 2010 Jun 16. Aleksandrov AA, Kota P, Aleksandrov LA, He L, Jensen T, Cui L, Gentzsch M, Dokholyan NV, Riordan JR
Regulatory insertion removal restores maturation, stability and function of DeltaF508 CFTR.
J Mol Biol. 2010 Aug 13;401(2):194-210. Epub 2010 Jun 16., 2010-08-13 [PMID:20561529]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) epithelial anion channel is a large multidomain membrane protein that matures inefficiently during biosynthesis. Its assembly is further perturbed by the deletion of F508 from the first nucleotide-binding domain (NBD1) responsible for most cystic fibrosis. The mutant polypeptide is recognized by cellular quality control systems and is proteolyzed. CFTR NBD1 contains a 32-residue segment termed the regulatory insertion (RI) not present in other ATP-binding cassette transporters. We report here that RI deletion enabled F508 CFTR to mature and traffic to the cell surface where it mediated regulated anion efflux and exhibited robust single chloride channel activity. Long-term pulse-chase experiments showed that the mature DeltaRI/DeltaF508 had a T(1/2) of approximately 14 h in cells, similar to the wild type. RI deletion restored ATP occlusion by NBD1 of DeltaF508 CFTR and had a strong thermostabilizing influence on the channel with gating up to at least 40 degrees C. None of these effects of RI removal were achieved by deletion of only portions of RI. Discrete molecular dynamics simulations of NBD1 indicated that RI might indirectly influence the interaction of NBD1 with the rest of the protein by attenuating the coupling of the F508-containing loop with the F1-like ATP-binding core subdomain so that RI removal overcame the perturbations caused by F508 deletion. Restriction of RI to a particular conformational state may ameliorate the impact of the disease-causing mutation.

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No. Sentence Comment
154 HEK 293 cells were transiently transfected with Cys-less ΔF508 CFTR with Cys pairs introduced at the CL2-NBD2 (C276-Q1280C) or CL4- NBD1 (V510C-G1069C) interfaces in the absence or presence of ΔRI. Login to comment

[hide] Allosteric modulation balances thermodynamic stabi... J Mol Biol. 2012 May 25;419(1-2):41-60. Epub 2012 Mar 8. Aleksandrov AA, Kota P, Cui L, Jensen T, Alekseev AE, Reyes S, He L, Gentzsch M, Aleksandrov LA, Dokholyan NV, Riordan JR
Allosteric modulation balances thermodynamic stability and restores function of DeltaF508 CFTR.
J Mol Biol. 2012 May 25;419(1-2):41-60. Epub 2012 Mar 8., [PMID:22406676]

Abstract [show]
Most cystic fibrosis is caused by a deletion of a single residue (F508) in CFTR (cystic fibrosis transmembrane conductance regulator) that disrupts the folding and biosynthetic maturation of the ion channel protein. Progress towards understanding the underlying mechanisms and overcoming the defect remains incomplete. Here, we show that the thermal instability of human DeltaF508 CFTR channel activity evident in both cell-attached membrane patches and planar phospholipid bilayers is not observed in corresponding mutant CFTRs of several non-mammalian species. These more stable orthologs are distinguished from their mammalian counterparts by the substitution of proline residues at several key dynamic locations in first N-terminal nucleotide-binding domain (NBD1), including the structurally diverse region, the gamma-phosphate switch loop, and the regulatory insertion. Molecular dynamics analyses revealed that addition of the prolines could reduce flexibility at these locations and increase the temperatures of unfolding transitions of DeltaF508 NBD1 to that of the wild type. Introduction of these prolines experimentally into full-length human DeltaF508 CFTR together with the already recognized I539T suppressor mutation, also in the structurally diverse region, restored channel function and thermodynamic stability as well as its trafficking to and lifetime at the cell surface. Thus, while cellular manipulations that circumvent its culling by quality control systems leave DeltaF508 CFTR dysfunctional at physiological temperature, restoration of the delicate balance between the dynamic protein's inherent stability and channel activity returns a near-normal state.

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No. Sentence Comment
155 Using an otherwise Cys-less construct, we had previously observed methanethiosulfonate-mediated cross-linking between V510C and G1069C in WT CFTR.29,33 Figure 7 shows similar cross-linking of this pair of residues in ΔF/4PT CFTR, providing evidence that the stabilization of ΔF508 NBD1 can Fig. 6. Login to comment
178 HEK293 cells were transiently transfected with Cys-less CFTR or Cys-less ΔF508-CFTR in the presence or absence of the 4PT mutations (S422P/S434P/S492P/A534P/I539T), with the Cys pair V510C/G1069C introduced at the CL4/NBD1 interface. Login to comment
279 Briefly, HEK cells transiently expressing Cys-less CFTR constructs with V510C and G1069C substitutions on the WT or ΔF/4PT CFTR basis grown on 35-mm tissue culture dishes were harvested, washed twice in PBS, and resuspended in 60 μl of PBS. Login to comment

[hide] Correctors of DeltaF508 CFTR restore global confor... FASEB J. 2013 Feb;27(2):536-45. doi: 10.1096/fj.12-216119. Epub 2012 Oct 26. He L, Kota P, Aleksandrov AA, Cui L, Jensen T, Dokholyan NV, Riordan JR
Correctors of DeltaF508 CFTR restore global conformational maturation without thermally stabilizing the mutant protein.
FASEB J. 2013 Feb;27(2):536-45. doi: 10.1096/fj.12-216119. Epub 2012 Oct 26., [PMID:23104983]

Abstract [show]
Most cystic fibrosis is caused by the deletion of a single amino acid (F508) from CFTR and the resulting misfolding and destabilization of the protein. Compounds identified by high-throughput screening to improve DeltaF508 CFTR maturation have already entered clinical trials, and it is important to understand their mechanisms of action to further improve their efficacy. Here, we showed that several of these compounds, including the investigational drug VX-809, caused a much greater increase (5- to 10-fold) in maturation at 27 than at 37 degrees C (<2-fold), and the mature product remained short-lived (T(1/2) approximately 4.5 h) and thermally unstable, even though its overall conformational state was similar to wild type, as judged by resistance to proteolysis and interdomain cross-linking. Consistent with its inability to restore thermodynamic stability, VX-809 stimulated maturation 2-5-fold beyond that caused by several different stabilizing modifications of NBD1 and the NBD1/CL4 interface. The compound also promoted maturation of several disease-associated processing mutants on the CL4 side of this interface. Although these effects may reflect an interaction of VX-809 with this interface, an interpretation supported by computational docking, it also rescued maturation of mutants in other cytoplasmic loops, either by allosteric effects or via additional sites of action. In addition to revealing the capabilities and some of the limitations of this important investigational drug, these findings clearly demonstrate that DeltaF508 CFTR can be completely assembled and evade cellular quality control systems, while remaining thermodynamically unstable. He, L., Kota, P., Aleksandrov, A. A., Cui, L., Jensen, T., Dokholyan, N. V., Riordan, J. R. Correctors of DeltaF508 CFTR restore global conformational maturation without thermally stabilizing the mutant protein.

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Sentences [show]
No. Sentence Comment
126 HEK293 cells were transiently transfected with Cys-less CFTR or Cys-less èc;F508 CFTR with Cys pairs 276C/Q1280C or V510C/G1069C, introduced at NBD2/CL2 and NBD1/CL4 interfaces, respectively (13). Login to comment