Double mutant cycle analysis identified a critical leucine residue in the IIS4S5 linker for the activation of the Ca(V)2.3 calcium channel.
J Biol Chem
; 286(31): 27197-205, 2011 Aug 05.
Article
em En
| MEDLINE
| ID: mdl-21652722
ABSTRACT
Mutations in distal S6 were shown to significantly alter the stability of the open state of Ca(V)2.3 (Raybaud, A., Baspinar, E. E., Dionne, F., Dodier, Y., Sauvé, R., and Parent, L. (2007) J. Biol. Chem. 282, 27944-27952). By analogy with K(V) channels, we tested the hypothesis that channel activation involves electromechanical coupling between S6 and the S4S5 linker in Ca(V)2.3. Among the 11 positions tested in the S4S5 linker of domain II, mutations of the leucine residue at position 596 were found to destabilize significantly the closed state with a -50 mV shift in the activation potential and a -20 mV shift in its charge-voltage relationship as compared with Ca(V)2.3 wt. A double mutant cycle analysis was performed by introducing pairs of glycine residues between S4S5 and S6 of Domain II. Strong coupling energies (ΔΔG(interact) > 2 kcal mol(-1)) were measured for the activation gating of 12 of 39 pairs of mutants. Leu-596 (IIS4S5) was strongly coupled with distal residues in IIS6 from Leu-699 to Asp-704. In particular, the double mutant L596G/I701G showed strong cooperativity with a ΔΔG(interact) ≈6 kcal mol(-1) suggesting that both positions contribute to the activation gating of the channel. Altogether, our results highlight the role of a leucine residue in S4S5 and provide the first series of evidence that the IIS4S5 and IIS6 regions are energetically coupled during the activation of a voltage-gated Ca(V) channel.
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Base de dados:
MEDLINE
Assunto principal:
Mutação Puntual
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Canais de Cálcio Tipo R
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Proteínas de Transporte de Cátions
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Leucina
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Canadá