title: Cooperative activation of the T-type CaV3.2 channel: interaction between Domains II and III.
abstract: 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.
authors: From the Département de Physiologie, Membrane Protein Research Group, Université de Montréal, Montréal, Quebec H3C 3J7, Canada.
authors: Pierre-Olivier
authors: PO
authors: Demers-Giroux
authors: Benoîte
authors: B
authors: Bourdin
authors: Rémy
authors: R
authors: Sauvé
authors: Lucie
authors: L
authors: Parent
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D020747:Calcium Channels, T-Type / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
chemical_list: C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type
keywords: Calcium Channels; Cut-open Oocyte; Electrophysiology; Epilepsy; Gating; Homology Modeling; Thermodynamics
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