Acetylcholinesterase: C-terminal domains, molecular forms and functional localization.

Acetylcholinesterase (AChE) possesses short C-terminal peptides that are not necessary for catalytic activity. These peptides belong to different classes (R, H, T, S) and define the post-translational processing and targeting of the enzyme. In vertebrates, subunits of type H (AChEH) and of type T (AChET) are the most important: AChEH subunits produce glycolipid (GPI)-anchored dimers and AChET subunits produce hetero-oligomeric forms such as membrane-bound tetramers in the mammalian brain (containing a 20 kDa hydrophobic protein) and asymmetric collagen-tailed forms in neuromuscular junctions (containing a specific collagen, ColQ). The T peptide allows the formation of tetrameric assemblies with a proline-rich attachment domain (PRAD) of collagen ColQ. These complex molecular structures condition the functional localization of the enzyme in the supramolecular architecture of cholinergic synapses.