Proceedings of the National Academy of Sciences · 1973 · 109 citations · 25 references
Life SciencesBiochemistryMolecular BiologyEnzyme MechanismEnzymologyProtein BiochemistryEnzyme BiophysicsEnzyme CharacterizationEnzyme KineticsEnzyme StructureOrganelle BiochemistryStructural EnzymologyElectric OrgansEnzyme Subunit CompositionIonic StrengthMarine Enzyme CharacterizationUltracentrifugation
Three purified molecular forms of acetylcholinesterase (EC 3.1.1.7) with sedimentation coefficients of 18 S, 14 S, and 11 S were studied by analytical ultracentrifugation and electron microscopy. The three species have molecular weights of (1.1 +/- 0.1) x 10(6), (7.5 +/- 1.5) x 10(5), and (3.35 +/- 0.25) x 10(5), respectively. Electron micrographs reveal that the 18S and 14S forms are asymmetric, composed of a head, containing a large number of subunits, and an elongated tail. The 11S form of acetylcholinesterase is apparently a tetrameric structure devoid of the tail. Maleylation of 18S and 14S acetylcholinesterases abolishes their tendency to aggregate at low ionic strength.
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