GTP regeneration influences interactions of microtubules, neurofilaments, and microtubule-associated proteins in vitro.
Interactions of microtubules, neurofilaments, and microtubule-associated proteins were investigated by turbidity and falling-ball viscometry measurements. We found evidence of endogenous GTPase activity in neurofilaments and microtubule-associated proteins (MAPs) in preparations that do not include urea or heat treatment, respectively. The absence or presence of either adenyl-5'-yl imidodiphosphonic acid or a GTP-regenerating system markedly influenced observed polymerization and gelation characteristics. Most significantly, the apparent viscosity of neurofilament and microtubule samples did not display a biphasic optimal MAP concentration profile when a GTP-regenerating system was operant. Likewise, GTP regeneration promoted the recovery of gelation following mechanical disruption of neurofilament/MAP/microtubule mixtures. These and other observations require some reassessment of proposed roles for microtubule-associated proteins in modulating neurofilament-microtubule interactions in vitro.
Flynn
G
G
Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610.
Purich
D L
DL
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D003599:Cytoskeleton / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000096:biosynthesis*; D007382:Intermediate Filaments / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D014783:Viscosity
D008869:Microtubule-Associated Proteins; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases