ATP Hydrolysis Activity and Polymerization State of Ribulose-1,5-Bisphosphate Carboxylase Oxygenase Activase (Do the Effects of Mg2+, K+, and Activase Concentrations Indicate a Functional Similarity to Actin?).

摘要: The ATPase activity and fluoresence of ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) activase were determined over a range MgCl2, KCl, concentrations. Both salts promoted ADP release from ATP intrinsic fluorescence enhancement by adenosine 5[prime]-[[gamma]-thio] triphosphate, but Mg2+ was about 10 times more effective than K+. both increased zero to saturation within the same K+ concentration ranges. At saturating concentrations (5 mM 22 K+), specific (turnover time, 1 s) maximal unaffected above [mu]M activase; below activase, decreased sharply. These responses are remarkably similar behavior actin. Intrinsic Rubisco reflects extent polymerization, showing that smaller oligomer or monomer present in low-salt is inactive hydrolysis. However, quenching 1-anilinonapthaline-8-sulfonate revealed triphosphate bind equally well at low- high-salt This consistent with an actin-like mechanism requiring dynamic equilibrium between oligomers for activation rate substrate-bound decarbamylated [mu]M. suggests large oligomeric form rather monomer, interacts when performing bound enzyme.