Lysis of cholinergic synaptosomes by an antiserum to choline acetyltransferase.

the present ")Cd n.m.r. data suggest that phospholipase C contains three classes of metal binding site. Type I, which is a single site buried somewhat in the structure, has a marked preference for Zn2+. This site has the highest affinity for divalent metal ions. Type I1 is a single site of somewhat lower affinity for divalent metal ions and shows a lesser preference for Zn2+ than the type I site and is more readily perturbed. The properties of the type I1 site are influenced by the particular metal ion bound in the type I site. Type 111 are much weaker binding sites for divalent metal ions and presumably exist on the surface of the enzyme. X-ray crystallographic analysis shows that in the enzyme type I and type I1 sites are approx. 0.5nm apart (E. Hough, L. Hansen & C. Little, unpublished work). Metal ions bound at the type I1 and type 111 sites are perturbed by the presence of Iand it is of interest to note that Iis a powerful inhibitor of this enzyme (Aakre 8c Little, 1982).