Multiple Molecular Forms of Acetylcholinesterase from Human Erythrocyte Membranes. Interconversion and Subunit Composition of Forms Separated by Density Gradient Centrifugation in a Zonal Rotor

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Abstract
Quantitative separation of eight multiple molecular forms of acetylcholinesterase isolated from human erythrocyte membranes was accomplished by sucrose density gradient centrifugation in a zonal rotor. Hydrodynamic properties of the four most abundant oligomers were investigated by analytical ultracentrifugation. The S20, w values obtained for these components ranged from 12.5 S to 19.0 S with corresponding molecular weights between 500000 and 1131000. These oligomers are built up of 6-14 subunits. Analysis of each isolated homogenous form after storage for 6 months at 4 °C revealed interconversion into the original eight components. Upon addition of Triton X-100 the oligomers disaggregate to yield a single 7-S form, which reaggregates upon removal of the detergent. Such reaggregation can be prevented by chaotropic ions indicating that hydrophobic interactions are important in the formation of these oligomeric forms.