Structural basis for alpha-conotoxin potency and selectivity.
Parkinson's disease is a debilitating movement disorder characterized by altered levels of alpha(6)beta(2) * ( * indicates the possible presence of additional subunits) nicotinic acetylcholine receptors (nAChRs) localized on presynaptic striatal catecholaminergic neurons. alpha-Conotoxin MII (alpha-CTx MII) is a highly useful ligand to probe alpha(6)beta(2) nAChRs structure and function, but it does not discriminate among closely related alpha(6) * nAChR subtypes. Modification of the alpha-CTx MII primary sequence led to the identification of alpha-CTx MII[E11A], an analog with 500-5300-fold discrimination between alpha(6) * subtypes found in both human and non-human primates. alpha-CTx MII[E11A] binds most strongly (femtomolar dissociation constant) to the high affinity alpha(6) nAChR, a subtype that is selectively lost in Parkinson's disease. Here, we present the three-dimensional solution structure for alpha-CTx MII[E11A] as determined by two-dimensional (1)H NMR spectroscopy to 0.13+/-0.09A backbone and 0.45+/-0.08A heavy atom root-mean-square deviation from mean structure. Structural comparisons suggest that the increased hydrophobic area of alpha-CTx MII[E11A] relative to other members of the alpha-CTx family may be responsible for its exceptionally high affinity for alpha6alpha4beta2 * nAChR as well as discrimination between alpha(6)beta(2) and alpha(3)beta(2) containing nAChRs. This finding may enable the rational design of novel peptide analogs that demonstrate enhanced specificity for alpha(6) * nAChR subunit interfaces and provide a means to better understand nAChR structural determinants that modulate brain dopamine levels and the pathophysiology of Parkinson's disease.
Turner
Matt
M
Department of Chemistry and Biochemistry, Boise State University, ID 83725-1520, USA.
Eidemiller
Seth
S
Martin
Bryan
B
Narver
Andrew
A
Marshall
Joshua
J
Zemp
Logan
L
Cornell
Kenneth A
KA
McIntosh
J Michael
JM
McDougal
Owen M
OM
D000595:Amino Acid Sequence; D020916:Conotoxins / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D018733:Nicotinic Antagonists / Q000737:chemistry* / Q000494:pharmacology; D010300:Parkinson Disease / Q000503:physiopathology; D011485:Protein Binding; D020033:Protein Isoforms; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000378:metabolism
D020916:Conotoxins; D018733:Nicotinic Antagonists; D020033:Protein Isoforms; D011978:Receptors, Nicotinic; C098872:alpha-conotoxin MII