Heat capacity microcalorimetry of the in vitro reconstitution of calf brain microtubules.
The self-assembly of calf brain tubulin, purified by the modified Weisenberg procedure, was examined in an adiabatic differential heat capacity microcalorimeter. Tubulin solutions at concentrations between 6 and 17 mg/mL were heated from 8 to 40 degrees C at heating rates between 0.1 and 1.0 deg/min in a pH 7.0 phosphate buffer containing 1 X 10(-3) M GTP, 1.6 X 10(-2) M MgCl2, and 3.4 M glycerol. The heat capacity change, deltaCp of the microtubule growth reaction was found to be -1600 +/- 500 cal/(deg mol) per 110 000 molecular weight tubulin dimer incorporated into microtubules, in agreement with the reported van't Hoff deltaCp value of -1500 cal/(deg mol) [Lee, J.C., & Timasheff, S.N. (1977) Biochemistry 16, 1754-1765]. The assembly reaction is characterized by a complex heat uptake pattern comprising both endothermic and exothermic processes.
D000818:Animals; D001921:Brain / Q000378:metabolism; D002151:Calorimetry; D002417:Cattle; D006023:Glycoproteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008970:Molecular Weight; D009391:Nephelometry and Turbidimetry; D009419:Nerve Tissue Proteins / Q000378:metabolism; D013816:Thermodynamics; D014404:Tubulin / Q000378:metabolism*
D006023:Glycoproteins; D009419:Nerve Tissue Proteins; D014404:Tubulin