5xgl
From Proteopedia
Co-crystal structure of Ac-AChBPP in complex with alpha-conotoxin LvIA
Structural highlights
Function[CAIA_CONLI] Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin blocks alpha-3-beta-2/CHRNA3-CHRNB2 nAChR with high selectivity (IC(50)=8.67 nM (on rat) and 17.5 (on human)) (PubMed:24398291). Has also weaker activity on alpha-6/alpha-3-beta-2-beta-3 (CHRNA6/CHRNA3-CHRNB2-CHRNB3) (IC(50)=108 nM (on rat)), alpha-6/alpha-3-beta-4 (CHRNA6/CHRNA3-CHRNB4) (IC(50)=121 nM (on rat)), alpha-3-beta-4 (CHRNA3-CHRNB4) (IC(50)=148 nM (on rat)), and alpha-7/CHRNA7 nAChRs (IC(50)=3000 nM (on rat)) (PubMed:24398291). When tested on mouse with hot-plate tests, this toxin significantly increases the base pain threshold and shows analgesic effects (PubMed:26742048).[1] [2] Publication Abstract from PubMedThe alpha3* nAChRs, which are considered to be promising drug targets for problems such as pain, addiction, cardiovascular function, cognitive disorders etc., are found throughout the central and peripheral nervous system. The alpha-conotoxin (alpha-CTx) LvIA has been identified as the most selective inhibitor of alpha3beta2 nAChRs known to date, and it can distinguish the alpha3beta2 nAChR subtype from the alpha6/alpha3beta2beta3 and alpha3beta4 nAChR subtypes. However, the mechanism of its selectivity towards alpha3beta2, alpha6/alpha3beta2beta3, and alpha3beta4 nAChRs remains elusive. Here we report the co-crystal structure of LvIA in complex with Aplysia californica acetylcholine binding protein (Ac-AChBP) at a resolution of 3.4 A. Based on the structure of this complex, together with homology modeling based on other nAChR subtypes and binding affinity assays, we conclude that Asp-11 of LvIA plays an important role in the selectivity of LvIA towards alpha3beta2 and alpha3/alpha6beta2beta3 nAChRs by making a salt bridge with Lys-155 of the rat alpha3 subunit. Asn-9 lies within a hydrophobic pocket that is formed by Met-36, Thr-59, and Phe-119 of the rat beta2 subunit in the alpha3beta2 nAChR model, revealing the reason for its more potent selectivity towards the alpha3beta2 nAChR subtype. These results provide molecular insights that can be used to design ligands that selectively target alpha3beta2 nAChRs, with significant implications for the design of new therapeutic alpha-CTxs. The crystal structure of Ac-AChBP in complex with alpha-conotoxin LvIA reveals the mechanism of its selectivity towards different nAChR subtypes.,Xu M, Zhu X, Yu J, Yu J, Luo S, Wang X Protein Cell. 2017 Sep;8(9):675-685. doi: 10.1007/s13238-017-0426-2. Epub 2017, Jun 5. PMID:28585176[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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