title: Identification of a MAP 2-like ATP-binding protein associated with axoplasmic vesicles that translocate on isolated microtubules.
abstract: Axoplasmic vesicles were purified and observed to translocate on isolated microtubules in an ATP-dependent, trypsin-sensitive manner, implying that ATP-binding polypeptides essential for force generation were present on the vesicle surface. To identify these proteins [alpha 32P]8-azidoadenosine 5'-triphosphate ([alpha 32P]8-N3ATP), a photoaffinity analogue of ATP, was used. The results presented here identify and characterize a vesicle-associated polypeptide having a relative molecular mass of 292 kD that bound [alpha 32P]8-N3ATP. The incorporation of label is ultraviolet light-dependent and ATP-sensitive. Moreover, the 292-kD polypeptide could be isolated in association with vesicles or microtubules, depending on the conditions used, and the data indicate that the 292-kD polypeptide is similar to mammalian brain microtubule-associated protein 2 (MAP 2) for the following reasons: The 292-kD polypeptide isolated from either squid axoplasm or optic lobe cross-reacts with antiserum to porcine brain MAP 2. Furthermore, it purifies with taxol-stabilized microtubules and is released with salt. Based on these characteristics, the 292-kD polypeptide is distinct from the known force-generating molecules myosin and flagellar dynein, as well as the 110-130-kD kinesin-like polypeptides that have recently been described (Brady, S. T., 1985, Nature (Lond.), 317:73-75; Vale, R. D., T. S. Reese, and M. P. Sheetz, 1985b, Cell, 42:39-50; Scholey, J. M., M. E. Porter, P. M. Grissom, and J. R. McIntosh, 1985, Nature (Lond.), 318:483-486). Because the 292-kD polypeptide binds ATP and is associated with vesicles that translocate on purified MAP-free microtubules in an ATP-dependent fashion, it is therefore believed to be involved in vesicle-microtubule interactions that promote organelle motility.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000345:Affinity Labels; D000818:Animals; D049832:Decapodiformes; D007122:Immunoelectrophoresis; D016547:Kinesins; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification*; D008870:Microtubules / Q000032:analysis*; D009068:Movement; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009899:Optic Lobe, Nonmammalian / Q000032:analysis; D012617:Sea Urchins
chemical_list: D000345:Affinity Labels; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D000255:Adenosine Triphosphate; D016547:Kinesins