Abstract
α-Conotoxin MII, a peptide toxin isolated from Conus magus, antagonizes a subset of neuronal nicotinic receptors. Rat α3β2 receptors, expressed in Xenopus oocytes, are blocked with an IC50 of 3.7 ± 0.3 nM. To identify structural features that determine toxin potency, a series of alanine-substituted toxins were synthesized and tested for the ability to block the function of α3β2 receptors. Circular dichroism and protein modeling were used to assess the structural integrity of the mutant toxins. Three residues were identified as major determinants of toxin potency. Replacement of asparagine 5, proline 6, or histidine 12 with alanine resulted in >2700-fold, 700-fold, and ∼2700-fold losses in toxin potency, respectively. A decrease in pH improved toxin potency, while an increase in pH eliminated toxin blockade, suggesting that, in the active form of the toxin, histidine 12 is charged. The imidazole ring of histidine 12 protrudes from one side, while asparagine 5 and proline 6 are located at the opposite end of the toxin structure. The side chains of these three residues are exposed on the surface of the toxin, suggesting that they directly interact with the α3β2 receptor.
| Original language | English |
|---|---|
| Pages (from-to) | 2732-2737 |
| Number of pages | 6 |
| Journal | Biochemistry |
| Volume | 43 |
| Issue number | 10 |
| DOIs | |
| State | Published - Mar 16 2004 |
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ASJC Scopus subject areas
- Biochemistry
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Determinants of Potency on α-Conotoxin MII, a Peptide Antagonist of Neuronal Nicotinic Receptors. / Everhart, Drew; Cartier, G. Edward; Malhotra, Arun; Gomes, Aldrin V.; McIntosh, J. Michael; Luetje, Charles W.
In: Biochemistry, Vol. 43, No. 10, 16.03.2004, p. 2732-2737.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Determinants of Potency on α-Conotoxin MII, a Peptide Antagonist of Neuronal Nicotinic Receptors
AU - Everhart, Drew
AU - Cartier, G. Edward
AU - Malhotra, Arun
AU - Gomes, Aldrin V.
AU - McIntosh, J. Michael
AU - Luetje, Charles W
PY - 2004/3/16
Y1 - 2004/3/16
N2 - α-Conotoxin MII, a peptide toxin isolated from Conus magus, antagonizes a subset of neuronal nicotinic receptors. Rat α3β2 receptors, expressed in Xenopus oocytes, are blocked with an IC50 of 3.7 ± 0.3 nM. To identify structural features that determine toxin potency, a series of alanine-substituted toxins were synthesized and tested for the ability to block the function of α3β2 receptors. Circular dichroism and protein modeling were used to assess the structural integrity of the mutant toxins. Three residues were identified as major determinants of toxin potency. Replacement of asparagine 5, proline 6, or histidine 12 with alanine resulted in >2700-fold, 700-fold, and ∼2700-fold losses in toxin potency, respectively. A decrease in pH improved toxin potency, while an increase in pH eliminated toxin blockade, suggesting that, in the active form of the toxin, histidine 12 is charged. The imidazole ring of histidine 12 protrudes from one side, while asparagine 5 and proline 6 are located at the opposite end of the toxin structure. The side chains of these three residues are exposed on the surface of the toxin, suggesting that they directly interact with the α3β2 receptor.
AB - α-Conotoxin MII, a peptide toxin isolated from Conus magus, antagonizes a subset of neuronal nicotinic receptors. Rat α3β2 receptors, expressed in Xenopus oocytes, are blocked with an IC50 of 3.7 ± 0.3 nM. To identify structural features that determine toxin potency, a series of alanine-substituted toxins were synthesized and tested for the ability to block the function of α3β2 receptors. Circular dichroism and protein modeling were used to assess the structural integrity of the mutant toxins. Three residues were identified as major determinants of toxin potency. Replacement of asparagine 5, proline 6, or histidine 12 with alanine resulted in >2700-fold, 700-fold, and ∼2700-fold losses in toxin potency, respectively. A decrease in pH improved toxin potency, while an increase in pH eliminated toxin blockade, suggesting that, in the active form of the toxin, histidine 12 is charged. The imidazole ring of histidine 12 protrudes from one side, while asparagine 5 and proline 6 are located at the opposite end of the toxin structure. The side chains of these three residues are exposed on the surface of the toxin, suggesting that they directly interact with the α3β2 receptor.
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UR - http://www.scopus.com/inward/citedby.url?scp=1542267785&partnerID=8YFLogxK
U2 - 10.1021/bi036180h
DO - 10.1021/bi036180h
M3 - Article
C2 - 15005608
AN - SCOPUS:1542267785
VL - 43
SP - 2732
EP - 2737
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 10
ER -