Characterization of a microtubule-stimulated adenosinetriphosphatase activity associated with microtubule gelation-contraction.
A microtubule-stimulated ATPase is associated with particles that are responsible for microtubule gelation-contraction in vitro. These particles have been proposed to be slow axonal transport, component a, particulates (SCAPs) [Weisenberg, R. C., Flynn, J. J., Gao, B., Awodi, S., Skee, F., Goodman, S., & Riederer, B. (1987) Science (Washington, D.C.) 238, 1119-1122]. The SCAP ATPase activity is stimulated approximately twofold by microtubules. The microtubule-stimulated ATPase activity correlates with the occurrence of microtubule gelation-contraction. Both microtubule-stimulated ATPase activity and microtubule gelation-contraction are inhibited by millimolar calcium, 0.3 M KCl plus 2 mM ethylenediaminetetraacetic acid (EDTA), 5 microM vanadate, and millimolar N-ethylmaleimide (NEM). Neither the ATPase activity nor microtubule gelation-contraction is affected by high magnesium concentrations (up to 8 mM) or by the anti-ATPase drugs ouabain, oligomycin, sodium azide, and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). Magnesium is required for both ATPase activity and microtubule gelation-contraction. Microtubule-stimulated hydrolysis of GTP, CTP, ITP, and UTP is less than 50% of ATP hydrolysis, and microtubule gelation-contraction is reduced in these nucleotides. On the basis of these results we propose that the microtubule-stimulated ATPase activity associated with SCAPs is a previously undescribed enzyme that is responsible for microtubule gelation-contraction in vitro and that is the likely motor for component a of slow axonal transport.
Gao
B C
BC
Department of Biology, Temple University, Philadelphia, Pennsylvania 19122.
Weisenberg
R C
RC
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D004492:Edetic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000494:pharmacology; D005782:Gels; D007700:Kinetics; D008870:Microtubules / Q000201:enzymology*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D005782:Gels; D014638:Vanadates; D011092:Polyethylene Glycols; D017830:Octoxynol; D004492:Edetic Acid; D000251:Adenosine Triphosphatases; D005033:Ethylmaleimide