ABCMdb

ABCC7 p.Glu267Ala

Predicted by SNAP2:	A: N (61%), C: D (63%), D: N (78%), F: D (80%), G: D (59%), H: D (75%), I: D (63%), K: D (59%), L: D (63%), M: D (53%), N: N (57%), P: D (71%), Q: N (66%), R: D (66%), S: N (66%), T: N (61%), V: D (53%), W: D (85%), Y: D (75%),
Predicted by PROVEAN:	A: N, C: D, D: N, F: D, G: N, H: N, I: D, K: N, L: D, M: D, N: N, P: N, Q: N, R: N, S: N, T: N, V: D, W: D, Y: D,

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Publications
[hide] CFTR: effect of ICL2 and ICL4 amino acids in close... J Cyst Fibros. 2013 Dec;12(6):737-45. doi: 10.1016/j.jcf.2013.02.002. Epub 2013 Mar 9. Billet A, Mornon JP, Jollivet M, Lehn P, Callebaut I, Becq F
CFTR: effect of ICL2 and ICL4 amino acids in close spatial proximity on the current properties of the channel.
J Cyst Fibros. 2013 Dec;12(6):737-45. doi: 10.1016/j.jcf.2013.02.002. Epub 2013 Mar 9., [PMID:23478129]

Abstract [show]
BACKGROUND: CFTR is the only ABC transporter functioning as a chloride (Cl(-)) channel. We studied molecular determinants, which might distinguish CFTR from standard ABC transporters, and focused on the interface formed by the intracellular loops from the membrane spanning domains. METHODS: Residues from ICL2 and ICL4 in close proximity were targeted, and their involvement in the functioning of CFTR was studied by whole cell patch clamp recording. RESULTS: We identified 2 pairs of amino acids, at the extremity of the bundle formed by the four intracellular loops, whose mutation i) decreases the Cl(-) current of CFTR (couple E267-K1060) or ii) increases it with a change of the electrophysiological signature (couple S263-V1056). CONCLUSIONS: These results highlight the critical role of these ICL residues in the assembly of the different domains and/or in the Cl(-) permeation pathway of CFTR.

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No. Sentence Comment
72 In order to change the properties of the side chains, we replaced each amino acid by a small, uncharged residue (mutants E267A-CFTR and K1060A-CFTR) or by an oppositely charged residue (mutants E267R-CFTR, K1060E-CFTR). Login to comment
86 100 200 -50 50 100 -100 100 100 100 200 C D B A I (pA/pF) I (pA/pF) I (pA/pF) V (mV) V (mV) V (mV) 5000pA 50ms E267R-K1060E E267A E267R K1060A K1060E E267A E267R wt E267R-K1060E K1060A K1060E ICL4 ICL2 K1060 E267 ICL1 ICL3 K1060 E267 ICL4 ICL2 ICL1 ICL3 % of maturation B C wt E267A E267R K1060A K1060E E267R-K1060E wt -50 50 100 -100 100 200 -50 50 100 -100 100 Fig. 2. Login to comment
93 Dotted lines represent a maturation similar to that of the wt protein (C, D) Whole cell chloride currents of HEK293 cells expressing wt-CFTR, E267A/R-, K1060A/Eor E267R-K1060E-CFTR mutants in presence of 10 bc;M Fsk. Login to comment
105 First, the presence of a small and uncharged residue at the E267 position (E267A mutant) decreased by approximately 50% the Cl-current density compared to wt. Login to comment
107 For K1060, irrespective of the replacement of the positively charged side chain by a small uncharged residue (K1060A mutant) or a negatively charged residue (K1060E mutant), the inward and outward Cl-current densities were 50-60% lower than the corresponding Cl-currents elicited by wt channels but similar to that of the E267A mutant. Login to comment
137 We observed that the abolition of one charged residue in the E267A or K1060A mutants induced a 50% diminution of the Cl-current density (Fig. 2). Login to comment

[hide] An electrostatic interaction at the tetrahelix bun... J Biol Chem. 2014 Oct 31;289(44):30364-78. doi: 10.1074/jbc.M114.595710. Epub 2014 Sep 4. Wang W, Roessler BC, Kirk KL
An electrostatic interaction at the tetrahelix bundle promotes phosphorylation-dependent cystic fibrosis transmembrane conductance regulator (CFTR) channel opening.
J Biol Chem. 2014 Oct 31;289(44):30364-78. doi: 10.1074/jbc.M114.595710. Epub 2014 Sep 4., [PMID:25190805]

Abstract [show]
The CFTR channel is an essential mediator of electrolyte transport across epithelial tissues. CFTR opening is promoted by ATP binding and dimerization of its two nucleotide binding domains (NBDs). Phosphorylation of its R domain (e.g. by PKA) is also required for channel activity. The CFTR structure is unsolved but homology models of the CFTR closed and open states have been produced based on the crystal structures of evolutionarily related ABC transporters. These models predict the formation of a tetrahelix bundle of intracellular loops (ICLs) during channel opening. Here we provide evidence that residues E267 in ICL2 and K1060 in ICL4 electrostatically interact at the interface of this predicted bundle to promote CFTR opening. Mutations or a thiol modifier that introduced like charges at these two positions substantially inhibited ATP-dependent channel opening. ATP-dependent activity was rescued by introducing a second site gain of function (GOF) mutation that was previously shown to promote ATP-dependent and ATP-independent opening (K978C). Conversely, the ATP-independent activity of the K978C GOF mutant was inhibited by charge- reversal mutations at positions 267 or 1060 either in the presence or absence of NBD2. The latter result indicates that this electrostatic interaction also promotes unliganded channel opening in the absence of ATP binding and NBD dimerization. Charge-reversal mutations at either position markedly reduced the PKA sensitivity of channel activation implying strong allosteric coupling between bundle formation and R domain phosphorylation. These findings support important roles of the tetrahelix bundle and the E267-K1060 electrostatic interaction in phosphorylation-dependent CFTR gating.

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No. Sentence Comment
256 These authors observed greater inhibition by a charge-reversal mutation than by a neutral substitution at the E267 position (E267R versus E267A), as we showed here in our more detailed mechanistic study. Login to comment