Turbidimetric studies of the in vitro assembly and disassembly of porcine neurotubules.

摘要: Abstract Turbidity measurements have been used to study the in vitro assembly and disassembly of porcine neurotubules. All were carried out with tubulin a purity higher than 80%. Tubules formed by this protein are so long that turbidity is insensitive length function only total mass high molecular weight material. Porcine shows critical concentration for about 0.2 mg/ml under optimal conditions, pH 6.6, 0.1 m -2-( N -morpholino)ethane sulfonic acid, 26 37 °C. Under these conditions essentially fully reversible presence excess GTP. The kinetics show an initial lag rates which strongly temperature dependent. Our samples dependence no more second order. apparent activation enthalpy 25 kcal/mol; reaction chain propagation step 21 kcal/mol. Disassembly negative −28 They independent tubule implying slow followed rapid depolymerization. At 20 °C, cycles polymerization depolymerization hysteresis effects though not or final states. This most easily explained postulating inactivation at 4 °C initiation complex assembly. Conditions reported producing state cannot assemble aqueous buffer unless nucleotides added. GTP, ATP ADP, but GDP, effective promoting An adenylate kinase impurity our preparation may be cause unusual effect. Whether it actually associated tubules unknown.