ABCMdb

ABCC8 p.Ala286Gly

Predicted by SNAP2:	C: N (61%), D: D (71%), E: D (71%), F: N (72%), G: N (72%), H: N (53%), I: D (63%), K: D (63%), L: D (63%), M: N (57%), N: N (57%), P: D (63%), Q: D (59%), R: D (53%), S: N (93%), T: N (82%), V: N (53%), W: N (53%), Y: N (61%),
Predicted by PROVEAN:	C: N, D: N, E: N, F: N, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: N, W: D, Y: N,

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Publications
[hide] Hydrophobic interactions as key determinants to th... J Biol Chem. 2009 Jan 2;284(1):389-403. Epub 2008 Nov 7. Garneau L, Klein H, Banderali U, Longpre-Lauzon A, Parent L, Sauve R
Hydrophobic interactions as key determinants to the KCa3.1 channel closed configuration. An analysis of KCa3.1 mutants constitutively active in zero Ca2+.
J Biol Chem. 2009 Jan 2;284(1):389-403. Epub 2008 Nov 7., [PMID:18996847]

Abstract [show]
In this study we present evidence that residue Val282 in the S6 transmembrane segment of the calcium-activated KCa3.1 channel constitutes a key determinant of channel gating. A Gly scan of the S6 transmembrane segment first revealed that the substitutions A279G and V282G cause the channel to become constitutively active in zero Ca2+. Constitutive activity was not observed when residues extending from Cys276 to Ala286, other than Ala279 and Val282, were substituted to Gly. The accessibility of Cys engineered at Val275 deep in the channel cavity was next investigated for the ion-conducting V275C/V282G mutant and closed V275C channel in zero Ca2+ using Ag+ as probe. These experiments demonstrated that internal Ag+ ions have free access to the channel cavity independently of the channel conducting state, arguing against an activation gate located at the S6 segment C-terminal end. Experiments were also conducted where Val282 was substituted by residues differing in size and/or hydrophobicity. We found a strong correlation between constitutive activity in zero Ca2+ and the hydrophobic energy for side chain burial. Single channel recordings showed finally that constitutive activation in zero Ca2+ is better explained by a model where the channel is locked in a low conducting state with a high open probability rather than resulting from a change in the open/closed energy balance that would favor channel openings to a full conducting state in the absence of Ca2+. We conclude that hydrophobic interactions involving Val282 constitute key determinants to KCa3.1 gating by modulating the ion conducting state of the selectivity filter through an effect on the S6 transmembrane segment.

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Sentences [show]
No. Sentence Comment
110 Results obtained with the V275C/A286G mutant are also included to illustrate the effect of MTSEAϩ on a nonconstitutively active channel, despite Ala286 facing the channel pore. Login to comment
119 D, constitutive activation was not seen with the V275C/A286G mutant, although Ala286 is facing the channel pore just like Ala279 and Val282 . Login to comment
123 The continuous application of MTSEAϩ onto the V275C/A286G mutant in Ca2ϩ free conditions (Fig. 5D) did not result in a detectable current inhibition (I0 ϭ IEGTA) confirming that V275C/A286G is not constitutively active. Login to comment
124 Furthermore, the absence of inhibition in this case cannot be attributed to cysteines at position 275 not being accessible to MTSEAϩ for the V275C/A286G mutant, because the subsequent addition of Ca2ϩ failed to initiate current activation, thus indicating covalent modification of V275C. Login to comment
212 D, an identical perfusion protocol applied to the V275C/A286G mutant failed to provide evidence of an MTSEAϩ -induced inhibition of I0, in accordance with V275C/A286G being closed in the absence of Ca2ϩ . Login to comment