QUATERNARY STRUCTURE OF ELECTRIC EEL ACETYLCHOLINESTERASE

Publisher Summary This chapter discusses a study to examine the quaternary structure of electric eel acetylcholinesterase. An 11S AChE preparation containing 50% monomers was labeled in its active sites with 3H-DFP, and a 14S+18S AChE preparation was similarly labeled with 14C-DFP. SDS-PAGE followed by differential counting of 3H and 14C in gel slices showed that the 3H-dimer was distinctly heavier than the 14C-dimer. No such difference was observed on the co-electrophoresis of 3H-DFP labeled 11S AChE with 14C-DFP-labeled 14S+18S AChE digested by trypsin. As the 14C-dimer represents the dimer that is not covalently attached to the tail, this experiment provides strong evidence that the 11S tetramer is an asymmetric structure in which one dimer contains a fragment of the tail. As this is the species remaining after tryptic digestion, presumably the other dimer is preferentially converted to monomers by trypsin. PAGE in the presence of β-mercaptoethanol reveals no significant difference in mobility of the labeled 80K components in the two preparations.