Electrophorus acetylcholinesterase. Biochemical and electron microscope characterization of low ionic strength aggregates

Abstract

The tailed molecules of Electrophorus (electric eel) acetylcholinesterase [EC 3.1.1.7] aggregated under conditions of low ionic strength. These aggregates were studied by sedimentation analysis and high-resolution EM. They consisted of bundles of at least 6 molecules, the tails of which are packed side by side, to form the core of the structure. Although aggregation is normally fully reversible, aggregates were irreversibly stabilized by methylene blue-sensitized photo-oxidation. This process was shown to consist of a singlet oxygen oxidation reaction and probably involved methionine or histidine residues. It did not modify the structural or hydrodynamic characteristics of the aggregates.