Green Brad R, Gajewiak Joanna, Chhabra Sandeep, Skalicky Jack J, Zhang Min-Min, Rivier Jean E, Bulaj Grzegorz, Olivera Baldomero M, Yoshikami Doju, Norton Raymond S
From the Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia, the Department of Biology, University of Utah, Salt Lake City, Utah 84112.
the Department of Biology, University of Utah, Salt Lake City, Utah 84112.
J Biol Chem. 2016 Mar 25;291(13):7205-20. doi: 10.1074/jbc.M115.697672. Epub 2016 Jan 27.
Cone 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 μO§-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 μO§-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 μO§-GVIIJ (GVIIJ[C24S]) and the results of structure-activity studies with synthetic μO§-GVIIJ variants. GVIIJ[C24S] adopts an inhibitor cystine knot structure, with two antiparallel β-strands stabilized by three disulfide bridges. The loop region linking the β-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 μO§-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 μO§-GVIIJ on a distinct surface of the peptide.
芋螺毒素是众所周知的电压门控钠通道阻滞剂，这一特性在生物学领域以及治疗神经性疼痛和神经疾病方面引起了广泛关注。尽管大多数芋螺毒素通道阻滞剂通过直接与通道结合并破坏其正常离子移动来发挥作用，但芋螺毒素μO§-GVIIJ的通道阻断作用却很独特，它既利用了与通道的有利结合相互作用，又通过分子间二硫键形成直接连接。二硫键交换是可能的，因为芋螺毒素μO§-GVIIJ含有一个S-半胱氨酸化的Cys-24残基，该残基能够与通道表面的游离半胱氨酸硫醇进行交换。在此，我们展示了μO§-GVIIJ类似物（GVIIJ[C24S]）的溶液结构以及合成的μO§-GVIIJ变体的构效关系研究结果。GVIIJ[C24S]采用抑制剂胱氨酸结结构，有两条反平行的β链由三个二硫键稳定。连接β链的环区（环4）中24位残基的构象使其能够与通道中假定的游离半胱氨酸（大鼠Nav1.2编号的Cys-910；位于位点8）结合。构效关系研究表明，位于环2且在空间上靠近24位残基的三个残基（Lys-12、Arg-14和Tyr-16）对功能活性也很重要。我们提出，μO§-GVIIJ与通道的相互作用不仅取决于通过Cys-24与通道位点8处的游离半胱氨酸形成二硫键连接，还取决于μO§-GVIIJ在肽的不同表面上关键残基的参与。
