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From Proteopedia
Solution structure of alpha-conotoxin SI
Structural highlights
FunctionCA1_CONST Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them (PubMed:3196703). Is active on muscle nAChR (IC(50)=113 nM on adult subtype (alpha-1-beta-1-gamma-delta/CHRNA1-CHRNB1-CHRNG-CHRND) and IC(50)=142 nM on fetal subtype (alpha-1-beta-1-delta-epsilon/CHRNA1-CHRNB1-CHRND-CHRNE)) (PubMed:35357806, PubMed:9174364). On mice muscle receptors, its higher affinity site is the alpha/delta nAChR subunit interface (PubMed:9174364). On Torpedo receptors, it does not distinguish between alpha/delta and alpha/gamma acetylcholine-binding sites (PubMed:9174364). In vivo, causes paralysis followed by death when injected into goldfish (PubMed:3196703). In contrast, has no effect on mice, when similar doses are intraperitoneally or intracerebrally injected (PubMed:3196703).[1] [2] [3] Publication Abstract from PubMedThe nuclear magnetic resonance solution structure of alpha-conotoxin SI has been determined at pH 4.2. The 36 lowest energy structures show that alpha-conotoxin SI exists in a single major solution conformation and is stabilized by six hydrogen bonds. Comparisons are made between the SI solution structure and the solution and crystal structures of alpha-conotoxin GI. Surprisingly, a high degree of similarity between the backbone conformations of the GI crystal and the SI solution structures is seen in the region of lowest sequence homology, namely residues Gly-8 to Ser-12. This similarity is more surprising when considering that in SI a proline replaces the Arg-9 found in GI. The correspondence in conformation in this region provides the definitive evidence that it is the loss of the arginine basic charge at residue 9 which determines the differences in toxicity between GI and SI, rather than any changes in conformation induced by the cyclic proline residue. Solution structure of alpha-conotoxin SI.,Benie AJ, Whitford D, Hargittai B, Barany G, Janes RW FEBS Lett. 2000 Jul 7;476(3):287-95. PMID:10913630[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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