In:
Biochemical Journal, Portland Press Ltd., Vol. 478, No. 14 ( 2021-07-30), p. 2843-2869
Abstract:
The interaction of insect-selective scorpion depressant β-toxins (LqhIT2 and Lqh-dprIT3 from Leiurus quinquestriatus hebraeus) with the Blattella germanica sodium channel, BgNav1-1a, was investigated using site-directed mutagenesis, electrophysiological analyses, and structural modeling. Focusing on the pharmacologically defined binding site-4 of scorpion β-toxins at the voltage-sensing domain II (VSD-II), we found that charge neutralization of D802 in VSD-II greatly enhanced the channel sensitivity to Lqh-dprIT3. This was consistent with the high sensitivity of the splice variant BgNav2-1, bearing G802, to Lqh-dprIT3, and low sensitivity of BgNav2-1 mutant, G802D, to the toxin. Further mutational and electrophysiological analyses revealed that the sensitivity of the WT = D802E & lt; D802G & lt; D802A & lt; D802K channel mutants to Lqh-dprIT3 correlated with the depolarizing shifts of activation in toxin-free channels. However, the sensitivity of single mutants involving IIS4 basic residues (K4E = WT & lt; & lt; R1E & lt; R2E & lt; R3E) or double mutants (D802K = K4E/D802K = R3E/D802K & gt; R2E/D802K & gt; R1E/D802K & gt; WT) did not correlate with the activation shifts. Using the cryo-EM structure of the Periplaneta americana channel, NavPaS, as a template and the crystal structure of LqhIT2, we constructed structural models of LqhIT2 and Lqh-dprIT3-c in complex with BgNav1-1a. These models along with the mutational analysis suggest that depressant toxins approach the salt-bridge between R1 and D802 at VSD-II to form contacts with linkers IIS1–S2, IIS3–S4, IIIP5–P1 and IIIP2–S6. Elimination of this salt-bridge enables deeper penetration of the toxin into a VSD-II gorge to form new contacts with the channel, leading to increased channel sensitivity to Lqh-dprIT3.
Type of Medium:
Online Resource
ISSN:
0264-6021
,
1470-8728
Language:
English
Publisher:
Portland Press Ltd.
Publication Date:
2021
detail.hit.zdb_id:
1473095-9
SSG:
12
