Molecular modeling of the collagen-like tail of asymmetric acetylcholinesterase

Abstract

The asymmetric form of acetylcholinesterase comprises three catalytic tetramers attached to ColQ, a collagen-like tail responsible for the anchorage of the enzyme to the synaptic basal lamina. ColQ is composed of an N-terminal domain which interacts with the catalytic subunits of the enzyme, a central collagen-like domain and a C-terminal globular domain. In particular, the collagen-like domain of ColQ contains two heparin-binding domains which interact with heparan sulfate proteoglycans in the basal lamina. A three-dimensional model of the collagen-like domain of the tail of asymmetric acetylcholinesterase was constructed. The model presents an undulated shape that results from the presence of a substitution and an insertion in the Gly-X-Y repeating pattern, as well as from low imino-acid regions. Moreover, this model permits the analysis of interactions between the heparin-binding domains of ColQ and heparin, and could also prove useful in the prediction of interaction domains with other putative basal lamina receptors.

Two Different Heparin-binding Domains in the Triple-helical Domain of ColQ, the Collagen Tail Subunit of Synaptic Acetylcholinesterase

“…2D, Table I). These results show that the recombinant rat A 12 AChE behaves exactly as the purified A 12 enzyme from Torpedo electric organ, so that Xenopus oocytes constitute a good expression system for A 12 AChE.…”

“…log[NaCl]), the NaCl concentration for 50% elution of the bound enzyme was obtained for each curve. This value was used in this study as a measure of the relative affinity of a given A 12 AChE mutant for heparin. In the different experiments, statistical analyses were performed using the unpaired Student's t test.…”

“…Other clusters of basic residues also exist within the N-and C-terminal noncollagenous domains of ColQ, and it has been suggested that the C-terminal domain could participate in binding to HSPGs 12 AChE from a heparin-agarose column using a linear NaCl gradient. AChE activity was measured in each fraction (symbols and solid line) as the NaCl concentration (dotted line).…”

“…1A). Each N-terminal domain organizes an AChE tetramer, so the triple-helical structure generates an A 12 or asymmetric AChE form with 12 catalytic subunits (3,4). The collagen domain is characterized by Gly-Xaa-Yaa repeats and a high proportion of the stabilizing proline and hydroxyproline residues.…”

“…We have characterized the structural properties of those putative heparin-binding domains (HBDs) by using molecular modeling and synthetic peptides (12)(13)(14). Here, we analyzed ColQ-heparin interactions by heparin affinity chromatography of the entire A 12 AChE, carrying different mutations in ColQ.…”