title: Microtubule-associated protein, MAP2, is a calcium-binding protein.
abstract: Calcium has been suggested to be an important element in the regulation of microtubule dynamics 'in vivo'. In this report we have analyzed the possibility that microtubule-associated protein 2 (MAP2) binds calcium. MAP2 was blue-stained with the cationic carbocyanine dye 'stains-all' in a similar way to that of calcium-binding proteins and bound 45Ca as estimated from dot-blotting experiments. The calcium-binding characteristics of MAP2, determined by equilibrium dialysis, indicated that MAP2 bound about 3 mol (n = 2.9 +/- 0.4) of calcium per mol of protein (Kd = (0.9 +/- 0.2).10(-5) M). Analysis of the Scatchard plots from equilibrium dialysis and dot-blot assays indicated that MAP2 also presented low-affinity calcium-binding sites (Kd = (0.3 +/- 0.2).10(-4) M). Incubation of nitrocellulose blots of proteolytically digested MAP2 with 45Ca indicated that the calcium-binding sites were located in the region that is not involved in the interaction with tubulin (projection region).
mesh_terms: D000818:Animals; D001665:Binding Sites; D001923:Brain Chemistry; D002132:Calcium Radioisotopes / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002232:Carbocyanines; D003101:Collodion; D003956:Dialysis; D008274:Magnesium / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D010434:Pepsin A / Q000378:metabolism; D010766:Phosphorylation; D013194:Staining and Labeling; D013552:Swine; D014404:Tubulin / Q000378:metabolism
chemical_list: D002132:Calcium Radioisotopes; D002135:Calcium-Binding Proteins; D002232:Carbocyanines; D008869:Microtubule-Associated Proteins; D014404:Tubulin; C012040:stains-all; D003101:Collodion; D010434:Pepsin A; D008274:Magnesium