Molecular Structures of Acetylcholinesterase from Electric Organ Tissue of the Electric Eel

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RESUMO

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) × 106, (7.5 ± 1.5) × 105, and (3.35 ± 0.25) × 105, 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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