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THREE-DIMENSIONAL SOLUTION STRUCTURE OF ALPHA-CONOTOXIN GID BY NMR SPECTROSCOPY
Structural highlights
FunctionCA1D_CONGE Alpha-conotoxins act on postsynaptic membranes, they bind to the nicotinic acetylcholine receptors (nAChR) and thus inhibit them. This toxin reversibly blocks alpha-3-beta-2 (IC(50)=3.1-5.1 nM), alpha-7 (IC(50)=4.5-5.1 nM), and alpha-4-beta-2 (IC(50)=128.6-390 nM) nAChRs.[1] [2] [3] Publication Abstract from PubMedUsing assay-directed fractionation of Conus geographus crude venom, we isolated alpha-conotoxin GID, which acts selectively at neuronal nicotinic acetylcholine receptors (nAChRs). Unlike other neuronally selective alpha-conotoxins, alpha-GID has a four amino acid N-terminal tail, gamma-carboxyglutamate (Gla), and hydroxyproline (O) residues, and lacks an amidated C terminus. GID inhibits alpha 7 and alpha 3 beta 2 nAChRs with IC(50) values of 5 and 3 nm, respectively and is at least 1000-fold less potent at the alpha 1 beta 1 gamma delta, alpha 3 beta 4, and alpha 4 beta 4 combinations. GID also potently inhibits the alpha 4 beta 2 subtype (IC(50) of 150 nm). Deletion of the N-terminal sequence (GID Delta 1-4) significantly decreased activity at the alpha 4 beta 2 nAChR but hardly affected potency at alpha 3 beta 2 and alpha 7 nAChRs, despite enhancing the off-rates at these receptors. In contrast, Arg(12) contributed to alpha 4 beta 2 and alpha 7 activity but not to alpha 3 beta 2 activity. The three-dimensional structure of GID is well defined over residues 4-19 with a similar motif to other alpha-conotoxins. However, despite its influence on activity, the tail appears to be disordered in solution. Comparison of GID with other alpha 4/7-conotoxins which possess an NN(P/O) motif in loop II, revealed a correlation between increasing length of the aliphatic side-chain in position 10 (equivalent to 13 in GID) and greater alpha 7 versus alpha 3 beta 2 selectivity. Isolation, structure, and activity of GID, a novel alpha 4/7-conotoxin with an extended N-terminal sequence.,Nicke A, Loughnan ML, Millard EL, Alewood PF, Adams DJ, Daly NL, Craik DJ, Lewis RJ J Biol Chem. 2003 Jan 31;278(5):3137-44. Epub 2002 Nov 4. PMID:12419800[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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