Employing NaChBac for cryo-EM analysis of toxin action on voltage-gated Na+ channels in nanodisc.
Proc Natl Acad Sci U S A
; 117(25): 14187-14193, 2020 06 23.
Article
em En
| MEDLINE
| ID: mdl-32513729
ABSTRACT
NaChBac, the first bacterial voltage-gated Na+ (Nav) channel to be characterized, has been the prokaryotic prototype for studying the structure-function relationship of Nav channels. Discovered nearly two decades ago, the structure of NaChBac has not been determined. Here we present the single particle electron cryomicroscopy (cryo-EM) analysis of NaChBac in both detergent micelles and nanodiscs. Under both conditions, the conformation of NaChBac is nearly identical to that of the potentially inactivated NavAb. Determining the structure of NaChBac in nanodiscs enabled us to examine gating modifier toxins (GMTs) of Nav channels in lipid bilayers. To study GMTs in mammalian Nav channels, we generated a chimera in which the extracellular fragment of the S3 and S4 segments in the second voltage-sensing domain from Nav1.7 replaced the corresponding sequence in NaChBac. Cryo-EM structures of the nanodisc-embedded chimera alone and in complex with HuwenToxin IV (HWTX-IV) were determined to 3.5 and 3.2 Å resolutions, respectively. Compared to the structure of HWTX-IV-bound human Nav1.7, which was obtained at an overall resolution of 3.2 Å, the local resolution of the toxin has been improved from â¼6 to â¼4 Å. This resolution enabled visualization of toxin docking. NaChBac can thus serve as a convenient surrogate for structural studies of the interactions between GMTs and Nav channels in a membrane environment.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Microscopia Crioeletrônica
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Nanoestruturas
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Canais de Sódio Disparados por Voltagem
Tipo de estudo:
Prognostic_studies
Limite:
Animals
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Humans
Idioma:
En
Ano de publicação:
2020
Tipo de documento:
Article