Résumé :
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The nervous tissue and muscles of mammals express the T splice variant of acetylcholinesterase (ACHET), characterized by its 40-residues C-terminal peptide (t peptide), which allows its association with anchoring proteins, the collagen ColQ and the transmembrane protein PRiMA, producing respectively collagen-tailed forms and membrane-bound tetramers. These interactions are important since they condition the functional anchoring of AChE in cholinergic tissues. The collagen-tailed forms are inserted in the basal lamina at neuromuscular junction, while the membrane-bound tetramers are anchored at the cell surface through the transmembrane domain of PRiMA. The membrane-bound tetramers represent the major enzyme species in the brain ; they are also expressed in muscles, where their level is regulated by exercise. The association of AChET subunits with ColQ has been extensively studied : it is based on an tight interaction between four t peptides and a proline-rich motif, called PRAD (?Proline-Rich Attachment Domain?), located in the N-terminal non collagenous region of ColQ. The structure of a complexe between synthetic t and PRAD peptides has been determined by cristallography. The association of AChET subunits with PRiMA appears similar because this transmembrane protein also contains a proline-rich motif, but there are significant differences in the number of prolines (8 in ColQ, 14 in PRiMA) and in the number and positions of cysteines that might form intercatenary disulfide bonds with the cysteine located near the C-terminus of the t peptides. Therefore, we have undertaken an analysis of the association of AChET with PRiMA. Using deletions and point mutations in PRiMA, we defined a minimal motif in PRiMA, which could associate with AChET subunits.
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