Circular dichroism studies of acetylcholinesterase conformation. Comparison of the 11 S and 5.6 S species and the differences induced by inhibitory ligands.
Circular dichroism studies were carried out in the vacuum ultraviolet region for 11 S and 5.6 S species of acetylcholinesterase from Torpedo. As the 5.6 S acetylcholinesterase forms larger oligomers in the absence of detergent, the CD spectrum was measured both with and without detergent. Secondary structure analysis of the CD spectrum for 11 S acetylcholinesterase shows 33% alpha-helix, 23% beta-sheet (14% antiparallel and 9% parallel), 17% turns and 26% other structure. Binding of edrophonium to the active site of 11 S acetylcholinesterase increases alpha-helix, while binding of propidium to the peripheral site increases beta-sheet. The beta-sheet content is slightly higher for 5.6 S than 11 S acetylcholinesterase in water. When the detergent is added to 5.6 S acetylcholinesterase, the 190 nm and 220 nm bands become less intense, although the analyses of the two spectra are similar. No significant change is observed for the 5.6 S form in either solvent on binding ligands. The prediction of both parallel and antiparallel beta-sheet suggests that at least one domain in these multidomain proteins belongs to the alpha/beta tertiary structural type.
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D003902:Detergents; D004491:Edrophonium / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D011487:Protein Conformation; D014101:Torpedo; D014867:Water
D003902:Detergents; D007527:Isoenzymes; D046911:Macromolecular Substances; D014867:Water; D004491:Edrophonium; D000110:Acetylcholinesterase