ABCMdb

ABCC7 p.Phe508Trp

ClinVar:	c.1523T>C , p.Phe508Ser ? , not provided c.1523T>G , p.Phe508Cys N , Benign
CF databases:	c.1521_1523delCTT , p.Phe508del D , CF-causing c.1523T>C , p.Phe508Ser (CFTR1) D , This mutation was found in a patient with CBAVD. c.1523T>G , p.Phe508Cys (CFTR1) ? ,
Predicted by SNAP2:	A: D (95%), C: D (75%), D: D (95%), E: D (95%), G: D (95%), H: D (95%), I: D (95%), K: D (95%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (95%), R: D (95%), S: D (95%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D,

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Publications
[hide] Side chain and backbone contributions of Phe508 to... Nat Struct Mol Biol. 2005 Jan;12(1):10-6. Epub 2004 Dec 26. Thibodeau PH, Brautigam CA, Machius M, Thomas PJ
Side chain and backbone contributions of Phe508 to CFTR folding.
Nat Struct Mol Biol. 2005 Jan;12(1):10-6. Epub 2004 Dec 26., [PMID:15619636]

Abstract [show]
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an integral membrane protein, cause cystic fibrosis (CF). The most common CF-causing mutant, deletion of Phe508, fails to properly fold. To elucidate the role Phe508 plays in the folding of CFTR, missense mutations at this position were generated. Only one missense mutation had a pronounced effect on the stability and folding of the isolated domain in vitro. In contrast, many substitutions, including those of charged and bulky residues, disrupted folding of full-length CFTR in cells. Structures of two mutant nucleotide-binding domains (NBDs) reveal only local alterations of the surface near position 508. These results suggest that the peptide backbone plays a role in the proper folding of the domain, whereas the side chain plays a role in defining a surface of NBD1 that potentially interacts with other domains during the maturation of intact CFTR.

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No. Sentence Comment
28 With the exception of F508W, all measured NBD1 proteins were capable of folding at 4 °C at near-100% efficiency as measured by the production of soluble conformers that were quantified by tryptophan fluorescence intensity or western blotting.In addition,all of the domains exhibited a temperature-dependence of refolding efficiency where overall yield in the soluble fraction decreased as temperature increased. Login to comment
38 However, when the F508W mutation was introduced onto the background of W496F, folding of the NBD1 was partially restored and the protein was capable of refolding with higher efficiency (>90% soluble) at 4 °C (Fig.1b). Login to comment
46 How does the isolated NBD accommodate such Temperature (ºC) 4 10 16 22 Fractionalyield 0.0 0.5 1.0 Temperature (ºC) 4 10 16 22 Temperature (ºC) 4 10 16 22 Wild type ∆F508 Wild type ∆F508 ̄ F508A ̄ F508M F508P F508W ͷ F508W W496F Wild type ∆F508 F508Q F508R F508D F508S a b c Figure 1 NBD1 folding efficiency as a function of folding temperature. Login to comment
52 (b) The F508W mutant, the only mutant that deviated markedly from the wild type, was rescued by the introduction of a second missense mutation, W496F. Login to comment
92 The known polymorphism F508C and the non-CF-causing variant F508S both showed measurable quantities of band C at steady-state levels, as would be expected for non-CF-causingsubstitutions.Thehydrophobicaminoacidsubstitutions F508I,F508W and F508Y did not produce substantial steady-state levels of band C as measured by western blotting, nor did the ionizable amino acid substitutions F508D, F508E, F508K, F508H or F508R. Login to comment
101 Notably, missense mutations other than F508W had little effect on either the folding or stability of the isolated NBD, suggesting that the peptide backbone at this locus is critical to NBD1 folding efficiency, whereas the side chain character is largely unimportant. Login to comment
104 The structures of NBD1 proteins also suggest a potential mechanism for the deleterious effects of the F508W substitution,as the phenylalanine side chain, although partially surface-exposed and accessible, interacts with surrounding residues.The nearest atom distances from both Trp496 and Met498 to Phe508 are ~4 Å.The additional physical size of the tryptophan side chain thus may not be accommodated by the local protein structure.However,when a second substitution,W496F,was introduced, the folding of the domain was rescued.Given the close proximity of both residues,theW496F substitution probably resolves a steric clash between the substituted tryptophan at position 508 and other local residues,consistent with the refolded protein reaching a native or near-native-state structure in vitro. Login to comment
113 W ild type ∆∆F508 F508 F508D F508K F508E F508R F508H F508S F508T F508N F508Q C B Charged Polar F508A F508C F508I F508L ∆F508 F508 W ild type C B F508W F508Y F508G F508P Hydrophobic F508M F508V ̅̆ ̆ ̅ Figure 3 Maturation of full-length CFTR mutants. 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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No. Sentence Comment
336 Collectively, the data indicate that F508del reduces the ability of NBD1 èc;RIèc;RE to homodimerize, probably by disrupting the Phe-508/Trp-496 side chain interaction that stabilizes the Q-loop. Login to comment