title: Interactions of a photoaffinity analog of GTP with the proteins of microtubules.
abstract: Tubulin dimers isolated from brain contain two GTP binding sites, a nonexchangeable site and an exchangeable site. To localize the exchangeable site, we used a photoaffinity analog of GTP, 8-azidoguanosine triphosphate (8-N3GTP), which supports tubulin polymerization in the absence of activating light. Photolysis of tubulin polymerized in the presence of 0.01 to 0.1 mM [beta, gamma-32P]8-N3GTP resulted in covalent incorporation of radioactivity only onto the beta monomer. Photolysis with 8-N3GTP also prevented any further repolymerization of the tubulin whereas like treatment in the presence of GTP had no effect. Preincubation of tubulin with GTP prevented photo-incorporation of [beta, gamma-32P]8-N3GTP whereas preincubation with ATP did not.
mesh_terms: D001665:Binding Sites; D006023:Glycoproteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D010782:Photolysis; D011485:Protein Binding; D014404:Tubulin / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D006023:Glycoproteins; D014404:Tubulin; D006160:Guanosine Triphosphate
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