Probing the ligand binding site of nicotinic receptors and binding proteins by hydrogen/deuterium exchange mass spectrometry reveals differences in binding by agonists, partial agonists, and antagonists

BIOL 48

Jianxin Shi1, Elizabeth A. Komives2, and Palmer W. Taylor1. (1) Department of Pharmacology, UC San Diego, 9500 Gilman Drive M/C 0636, La Jolla, CA 92093-0636, (2) Department of Chemistry and Biochemistry, UC San Diego, 9500 Gilman Drive, La Jolla, CA 92093
Recent crystal structures of acetylcholine binding protein (AChBP) have served as critical template for understanding the structure and conformation of the superfamily of pentameric ligand-gated ion channels. However, it remains unclear how protein dynamics contribute to the ligand activation of ion channels. H-D exchange mass spectrometry can directly examine the conformational changes upon agonist and antagonists association with AChBP in solution. In the apo-protein, two regions facing the active site at the subunit interface, loop C (175-193) and loop F (164-171), adopt highly flexible conformations. Agonists (epibatidine, lobeline, and anabaseine) all produce very similar exchange kinetics. By contrast, partial agonists (GST-21 and 4OH-MBA), alkaloid antagonists (d-tubocurarine and metocurine), and short and long peptidic antagonists (a-conotoxins and a-neurotoxins) all protect loop C to varying extents and with distinctive exchange kinetics, indicating discrete conformational states of AChBP. These data underscore the selective influence of pharmacologically different classes of nicotinic ligands on the dynamics state of the protein.
 

Protein Structure and Folding
4:30 PM-6:30 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Biological Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006