Orientation of -Neurotoxin at the Subunit Interfaces of the Nicotinic Acetylcholine Receptor
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- 作者：Siobhan Malany ; Hitoshi Osaka ; Steven M. Sine ; and Palmer Taylor
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：December 19, 2000
- 年：2000
- 卷：39
- 期：50
- 页码：15388 - 15398
- 全文大小：396K
- 年卷期：v.39,no.50(December 19, 2000)
- ISSN：1520-4995
文摘
The 
-neurotoxins are three-fingered peptide toxins that bind selectively at interfaces formedby the subunit and its associating subunit partner, 
, 
, or 
of the nicotinic acetylcholine receptor.Because the -neurotoxin from Naja mossambica mossambica I shows an unusual selectivity for the and over the subunit interface, residue replacement and mutant cycle analysis of paired residuesenabled us to identify the determinants in the and sequences governing -toxin recognition. Tocomplement this approach, we have similarly analyzed residues on the subunit face of the binding sitedictating specificity for -toxin. Analysis of the interface shows unique pairwise interactions betweenthe charged residues on the -toxin and three regions on the subunit located around residue Asp99,between residues Trp149 and Val153, and between residues Trp187 and Asp200. Substitutions of cationicresidues at positions between Trp149 and Val153 markedly reduce the rate of -toxin binding, and thesecationic residues appear to be determinants in preventing -toxin binding to 2, 3, and 4 subunitcontaining receptors. Replacement of selected residues in the -toxin shows that Ser8 on loop I and Arg33and Arg36 on the face of loop II, in apposition to loop I, are critical to the -toxin for association with the subunit. Pairwise mutant cycle analysis has enabled us to position residues on the concave face of thethree -toxin loops with respect to and subunit residues in the -toxin binding site. Binding of NmmI-toxin to the interface appears to have dominant electrostatic interactions not seen at the interface.
-neurotoxins are three-fingered peptide toxins that bind selectively at interfaces formedby the subunit and its associating subunit partner, , , or of the nicotinic acetylcholine receptor.Because the -neurotoxin from Naja mossambica mossambica I shows an unusual selectivity for the and over the subunit interface, residue replacement and mutant cycle analysis of paired residuesenabled us to identify the determinants in the and sequences governing -toxin recognition. Tocomplement this approach, we have similarly analyzed residues on the subunit face of the binding sitedictating specificity for -toxin. Analysis of the interface shows unique pairwise interactions betweenthe charged residues on the -toxin and three regions on the subunit located around residue Asp99,between residues Trp149 and Val153, and between residues Trp187 and Asp200. Substitutions of cationicresidues at positions between Trp149 and Val153 markedly reduce the rate of -toxin binding, and thesecationic residues appear to be determinants in preventing -toxin binding to 2, 3, and 4 subunitcontaining receptors. Replacement of selected residues in the -toxin shows that Ser8 on loop I and Arg33and Arg36 on the face of loop II, in apposition to loop I, are critical to the -toxin for association with the subunit. Pairwise mutant cycle analysis has enabled us to position residues on the concave face of thethree -toxin loops with respect to and subunit residues in the -toxin binding site. Binding of NmmI-toxin to the interface appears to have dominant electrostatic interactions not seen at the interface.