5e4t
Acetylcholinesterase Methylene Blue with PEG
Structural highlights
FunctionACES_TETCF Terminates signal transduction at the neuromuscular junction by rapid hydrolysis of the acetylcholine released into the synaptic cleft. May be involved in cell-cell interactions. Publication Abstract from PubMedStructure-based drug design utilizes apoprotein or complex structures retrieved from the PDB. >57% of crystallographic PDB entries were obtained with polyethylene glycols (PEGs) as precipitant and/or as cryoprotectant, but <6% of these report presence of individual ethyleneglycol oligomers. We report a case in which ethyleneglycol oligomers' presence in a crystal structure markedly affected the bound ligand's position. Specifically, we compared the positions of methylene blue and decamethonium in acetylcholinesterase complexes obtained using isomorphous crystals precipitated with PEG200 or ammonium sulfate. The ligands' positions within the active-site gorge in complexes obtained using PEG200 are influenced by presence of ethyleneglycol oligomers in both cases bound to W84 at the gorge's bottom, preventing interaction of the ligand's proximal quaternary group with its indole. Consequently, both ligands are approximately 3.0A further up the gorge than in complexes obtained using crystals precipitated with ammonium sulfate, in which the quaternary groups make direct pi-cation interactions with the indole. These findings have implications for structure-based drug design, since data for ligand-protein complexes with polyethylene glycol as precipitant may not reflect the ligand's position in its absence, and could result in selecting incorrect drug discovery leads. Docking methylene blue into the structure obtained with PEG200, but omitting the ethyleneglycols, yields results agreeing poorly with the crystal structure; excellent agreement is obtained if they are included. Many proteins display features in which precipitants might lodge. It will be important to investigate presence of precipitants in published crystal structures, and whether it has resulted in misinterpreting electron density maps, adversely affecting drug design. The impact of crystallization conditions on structure-based drug design: A case study on the methylene blue/acetylcholinesterase complex.,Dym O, Song W, Felder C, Roth E, Shnyrov V, Ashani Y, Xu Y, Joosten RP, Weiner L, Sussman JL, Silman I Protein Sci. 2016 Mar 14. doi: 10.1002/pro.2923. PMID:26990888[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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