2n8h
From Proteopedia
Structural basis for the inhibition of voltage-gated sodium channels with conotoxin-muOxi-GVIIJ
Structural highlights
FunctionO17J_CONGE Mu-conotoxins block voltage-gated sodium channels (Nav). This toxin (GVIIJ(SSG)) blocks Nav1.1/SCN1A (Kd=11 nM), Nav1.2/SCN2A (Kd=11 nM), Nav1.3/SCN3A (Kd=15 nM), Nav1.4/SCN4A (Kd=4.7 nM), Nav1.6/SCN8A (Kd=360 nM) and Nav1.7/SCN9A (Kd=41 nM) (PubMed:24497506, PubMed:26039939). It binds the channel at the newly described site 8, which is composed by two surfaces whose one contains a non-disulfide-bonded cysteine (which is free to covalently bind the toxin Cys-71) (PubMed:24497506). It is noteworthy that coexpression of subunits beta-2 or beta-4 (but not beta-1 or beta-3) protects rNav1.1-1.7 against block by the toxin, since these subunits (thanks to their extracellular domain) covalently bind to the key cysteine of the channel, thus preventing the covalent binding of the toxin (PubMed:24497506, PubMed:25632083).[1] [2] [3] [4] Publication Abstract from PubMedCone snail toxins are well known blockers of voltage-gated sodium channels, a property that is of broad interest in biology and therapeutically in treating neuropathic pain and neurological disorders. Although most conotoxin channel blockers function by direct binding to a channel and disrupting its normal ion movement, conotoxin muO section sign-GVIIJ channel blocking is unique, using both favorable binding interactions with the channel and a direct tether via an intermolecular disulfide bond. Disulfide exchange is possible because conotoxin muO section sign-GVIIJ contains anS-cysteinylated Cys-24 residue that is capable of exchanging with a free cysteine thiol on the channel surface. Here, we present the solution structure of an analog of muO section sign-GVIIJ (GVIIJ[C24S]) and the results of structure-activity studies with synthetic muO section sign-GVIIJ variants. GVIIJ[C24S] adopts an inhibitor cystine knot structure, with two antiparallel beta-strands stabilized by three disulfide bridges. The loop region linking the beta-strands (loop 4) presents residue 24 in a configuration where it could bind to the proposed free cysteine of the channel (Cys-910, rat NaV1.2 numbering; at site 8). The structure-activity study shows that three residues (Lys-12, Arg-14, and Tyr-16) located in loop 2 and spatially close to residue 24 were also important for functional activity. We propose that the interaction of muO section sign-GVIIJ with the channel depends on not only disulfide tethering via Cys-24 to a free cysteine at site 8 on the channel but also the participation of key residues of muO section sign-GVIIJ on a distinct surface of the peptide. Structural Basis for the Inhibition of Voltage-gated Sodium Channels by Conotoxin muO section sign-GVIIJ.,Green BR, Gajewiak J, Chhabra S, Skalicky JJ, Zhang MM, Rivier JE, Bulaj G, Olivera BM, Yoshikami D, Norton RS J Biol Chem. 2016 Mar 25;291(13):7205-20. doi: 10.1074/jbc.M115.697672. Epub 2016, Jan 27. PMID:26817840[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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