2XZ5

MMTS-modified Y53C mutant of Aplysia AChBP in complex with acetylcholine

Summary for 2XZ5

• Entry DOI: 10.2210/pdb2xz5/pdb
• Related: 2BR7 2BR8 2BYN 2BYP 2BYQ 2BYR 2BYS 2C9T 2UZ6 2W8E 2W8F 2W8G 2WN9 2WNC 2WNJ 2WNL 2WZY 2X00 2XNT 2XNU 2XNV 2XYS 2XYT 2XZ6
• Descriptor: SOLUBLE ACETYLCHOLINE RECEPTOR, ACETYLCHOLINE, CHLORIDE ION, ... (7 entities in total)
• Functional Keywords: receptor, amidation, conformational flexibility, conotoxin, neurotoxinnicotinic, postsynaptic neurotoxin, receptor/toxin
• Biological source: APLYSIA CALIFORNICA (CALIFORNIA SEA HARE)
• Total number of polymer chains: 5
• Total formula weight: 127231.87

Authors

Brams, M.,Gay, E.A.,Colon Saez, J.,Guskov, A.,van Elk, R.,van der Schors, R.C.,Peigneur, S.,Tytgat, J.,Strelkov, S.V.,Smit, A.B.,Yakel, J.L.,Ulens, C. (deposition date: 2010-11-23, release date: 2010-12-08, Last modification date: 2023-12-20)

Primary citation

Brams, M.,Gay, E.A.,Colon Saez, J.,Guskov, A.,Van Elk, R.,Van Der Schors, R.C.,Peigneur, S.,Tytgat, J.,Strelkov, S.V.,Smit, A.B.,Yakel, J.L.,Ulens, C.
Crystal Structures of a Cysteine-Modified Mutant in Loop D of Acetylcholine Binding Protein
J.Biol.Chem., 286:4420-, 2011

PubMed Abstract: Covalent modification of α7 W55C nicotinic acetylcholine receptors (nAChR) with the cysteine-modifying reagent [2-(trimethylammonium)ethyl] methanethiosulfonate (MTSET(+)) produces receptors that are unresponsive to acetylcholine, whereas methyl methanethiolsulfonate (MMTS) produces enhanced acetylcholine-gated currents. Here, we investigate structural changes that underlie the opposite effects of MTSET(+) and MMTS using acetylcholine-binding protein (AChBP), a homolog of the extracellular domain of the nAChR. Crystal structures of Y53C AChBP show that MTSET(+)-modification stabilizes loop C in an extended conformation that resembles the antagonist-bound state, which parallels our observation that MTSET(+) produces unresponsive W55C nAChRs. The MMTS-modified mutant in complex with acetylcholine is characterized by a contracted C-loop, similar to other agonist-bound complexes. Surprisingly, we find two acetylcholine molecules bound in the ligand-binding site, which might explain the potentiating effect of MMTS modification in W55C nAChRs. Unexpectedly, we observed in the MMTS-Y53C structure that ten phosphate ions arranged in two rings at adjacent sites are bound in the vestibule of AChBP. We mutated homologous residues in the vestibule of α1 GlyR and observed a reduction in the single channel conductance, suggesting a role of this site in ion permeation. Taken together, our results demonstrate that targeted modification of a conserved aromatic residue in loop D is sufficient for a conformational switch of AChBP and that a defined region in the vestibule of the extracellular domain contributes to ion conduction in anion-selective Cys-loop receptors.

PubMed: 21115477
DOI: 10.1074/JBC.M110.188730

Experimental method

X-RAY DIFFRACTION (2.8 Å)