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XB-ART-47959
J Biol Chem 2013 Oct 11;28841:29281-93. doi: 10.1074/jbc.M113.500975.
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Cooperative activation of the T-type CaV3.2 channel: interaction between Domains II and III.

Demers-Giroux PO , Bourdin B , Sauvé R , Parent L .


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T-type CaV3 channels are important mediators of Ca(2+) entry near the resting membrane potential. Little is known about the molecular mechanisms responsible for channel activation. Homology models based upon the high-resolution structure of bacterial NaV channels predict interaction between the S4-S5 helix of Domain II (IIS4-S5) and the distal S6 pore region of Domain II (IIS6) and Domain III (IIIS6). Functional intra- and inter-domain interactions were investigated with a double mutant cycle analysis. Activation gating and channel kinetics were measured for 47 single mutants and 20 pairs of mutants. Significant coupling energies (ΔΔG(interact) ≥ 1.5 kcal mol(-1)) were measured for 4 specific pairs of mutants introduced between IIS4-S5 and IIS6 and between IIS4-S5 and IIIS6. In agreement with the computer based models, Thr-911 in IIS4-S5 was functionally coupled with Ile-1013 in IIS6 during channel activation. The interaction energy was, however, found to be stronger between Val-907 in IIS4-S5 and Ile-1013 in IIS6. In addition Val-907 was significantly coupled with Asn-1548 in IIIS6 but not with Asn-1853 in IVS6. Altogether, our results demonstrate that the S4-S5 and S6 helices from adjacent domains are energetically coupled during the activation of a low voltage-gated T-type CaV3 channel.

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Species referenced: Xenopus laevis
Genes referenced: cacna1h cav3.1 cav3.2

References [+] :
Amaral, Exploring conformational states of the bacterial voltage-gated sodium channel NavAb via molecular dynamics simulations. 2012, Pubmed