ABCMdb

ABCC7 p.Ser495Pro

CF databases:	c.1484C>A , p.Ser495Tyr (CFTR1) ? ,
Predicted by SNAP2:	A: N (78%), C: D (59%), D: D (75%), E: D (75%), F: D (80%), G: D (63%), H: D (71%), I: D (75%), K: D (80%), L: D (75%), M: D (71%), N: D (63%), P: N (87%), Q: D (71%), R: D (80%), T: D (53%), V: D (71%), W: D (85%), Y: D (80%),
Predicted by PROVEAN:	A: N, C: N, D: N, E: N, F: D, G: N, H: D, I: D, K: N, L: D, M: D, N: N, P: N, Q: N, R: D, T: N, V: D, W: D, Y: D,

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Publications
[hide] Restoration of NBD1 thermal stability is necessary... J Mol Biol. 2015 Jan 16;427(1):106-20. doi: 10.1016/j.jmb.2014.07.026. Epub 2014 Jul 30. He L, Aleksandrov AA, An J, Cui L, Yang Z, Brouillette CG, Riordan JR
Restoration of NBD1 thermal stability is necessary and sufficient to correct F508 CFTR folding and assembly.
J Mol Biol. 2015 Jan 16;427(1):106-20. doi: 10.1016/j.jmb.2014.07.026. Epub 2014 Jul 30., [PMID:25083918]

Abstract [show]
Cystic fibrosis transmembrane conductance regulator (CFTR) (ABCC7), unique among ABC exporters as an ion channel, regulates ion and fluid transport in epithelial tissues. Loss of function due to mutations in the cftr gene causes cystic fibrosis. The most common cystic-fibrosis-causing mutation, the deletion of F508 (DeltaF508) from the first nucleotide binding domain (NBD1) of CFTR, results in misfolding of the protein and clearance by cellular quality control systems. The DeltaF508 mutation has two major impacts on CFTR: reduced thermal stability of NBD1 and disruption of its interface with membrane-spanning domains (MSDs). It is unknown if these two defects are independent and need to be targeted separately. To address this question, we varied the extent of stabilization of NBD1 using different second-site mutations and NBD1 binding small molecules with or without NBD1/MSD interface mutation. Combinations of different NBD1 changes had additive corrective effects on F508 maturation that correlated with their ability to increase NBD1 thermostability. These effects were much larger than those caused by interface modification alone and accounted for most of the correction achieved by modifying both the domain and the interface. Thus, NBD1 stabilization plays a dominant role in overcoming the DeltaF508 defect. Furthermore, the dual target approach resulted in a locked-open ion channel that was constitutively active in the absence of the normally obligatory dependence on phosphorylation by protein kinase A. Thus, simultaneous targeting of both the domain and the interface, as well as being non-essential for correction of biogenesis, may disrupt normal regulation of channel function.

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No. Sentence Comment
72 2PT, S492P/ A534P/I539T; 3PT, 2PT + S495P. Login to comment
93 In addition to the S492P substitution found in three non-mammalian species that are relatively insensitive to the destabilizing influence of the ƊF508 mutation [13], we also included a second Q-loop proline substitution, S495P present in shark CFTR. Login to comment
97 The S495P substitution alone in the isolated NBD1 of human CFTR caused the largest increase in Tm (5.99 &#b1; 0.33 &#b0;C) of any single change tested (Fig. 2a, lower panel). Login to comment
98 Therefore, we compared the effect of S495P with that of other NBD1 stabilizing mutations on the maturation of ƊF508 CFTR. Login to comment
99 As shown in Fig. 2b, the S495P substitution in ƊF508 CFTR resulted in substantial maturation. Login to comment
101 Combination of I539T with S495P, however, did cause a further increase in maturation and the effects of the two proline substitutions also were additive. Login to comment
179 Strikingly, the introduction of a proline residue at position 495 (S495P) in the Q-loop was found to cause the largest increase in the domain Tm and have the strongest restorative effect on maturation of the full-length protein of any single NBD1 second-site change and its influence was additive with others (Fig. 2). Login to comment
191 As demonstrated in the current work the S495P mutation, two residues C-terminal of the Q-loop glutamine have the greatest impact. Login to comment

[hide] Deletion of Phenylalanine 508 in the First Nucleot... J Biol Chem. 2015 Sep 18;290(38):22862-78. doi: 10.1074/jbc.M115.641134. Epub 2015 Jul 6. Chong PA, Farber PJ, Vernon RM, Hudson RP, Mittermaier AK, Forman-Kay JD
Deletion of Phenylalanine 508 in the First Nucleotide-binding Domain of the Cystic Fibrosis Transmembrane Conductance Regulator Increases Conformational Exchange and Inhibits Dimerization.
J Biol Chem. 2015 Sep 18;290(38):22862-78. doi: 10.1074/jbc.M115.641134. Epub 2015 Jul 6., [PMID:26149808]

Abstract [show]
Deletion of Phe-508 (F508del) in the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) results in destabilization of the domain, intramolecular interactions involving the domain, and the entire channel. The destabilization caused by F508del manifests itself in defective channel processing and channel gating defects. Here, we present NMR studies of the effect of F508del and the I539T stabilizing mutation on NBD1 dynamics, with a view to understanding these changes in stability. Qualitatively, F508del NMR spectra exhibit significantly more peak broadening than WT spectra due to the enhanced intermediate time scale (millisecond to microsecond) motions in the mutant. Unexpectedly, studies of fast (nanosecond to picosecond) motions revealed that F508del NBD1 tumbles more rapidly in solution than WT NBD1. Whereas F508del tumbles at a rate nearly consistent with the monomeric state, the WT protein tumbles significantly more slowly. Paramagnetic relaxation enhancement experiments confirm that NBD1 homodimerizes in solution in the expected head-to-tail orientation. NMR spectra of WT NBD1 reveal significant concentration-dependent chemical shift perturbations consistent with NBD1 dimerization. Chemical shift analysis suggests that the more rapid tumbling of F508del is the result of an impaired ability to dimerize. Based on previously published crystal structures and NMR spectra of various NBD1 mutants, we propose that deletion of Phe-508 affects Q-loop conformational sampling in a manner that inhibits dimerization. These results provide a potential mechanism for inhibition of channel opening by F508del and support the dimer interface as a target for cystic fibrosis therapeutics.

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Sentences [show]
No. Sentence Comment
386 Other published Q-loop segment suppressor mutations such as S492P and S495P (21, 29) are also likely to modulate NBD dimerization. Login to comment