A novel microtubule-associated protein from mammalian nerve shows ATP-sensitive binding to microtubules.
We report the isolation of a protein from mammalian nerve which shows ATP-sensitive binding to microtubules and ATPase activity. This protein, which we have designated HMW4, was prepared from bovine spinal nerve roots by microtubule affinity and ATP-induced release, and was further purified by sucrose density gradient centrifugation. It is a high molecular weight protein with a denatured Mr of 315,000, a Stokes radius of 90 A, and a sedimentation value of approximately 19S. It can be resolved electrophoretically from the well-characterized bovine brain microtubule-associated proteins (MAPs) and also appears to be distinct from MAP 1C. HMW4 has a vanadate-sensitive and azide-insensitive ATPase activity which averages 20 nmol Pi/min per mg protein and is different from dynein and myosin ATPases. HMW4 prepared on sucrose gradients exhibits binding to MAP-free microtubules in the absence of ATP which is reduced by ATP addition. Assayed by darkfield microscopy, HMW4 causes bundling of MAP-free microtubules which is reversed by ATP addition.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001386:Azides / Q000494:pharmacology; D001923:Brain Chemistry; D002417:Cattle; D008869:Microtubule-Associated Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D019810:Sodium Azide; D013127:Spinal Nerves / Q000032:analysis*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
D001386:Azides; D008869:Microtubule-Associated Proteins; C050362:microtubule-associated protein HMW4; D014639:Vanadium; D014638:Vanadates; D000255:Adenosine Triphosphate; D019810:Sodium Azide