Arrhenius activation energy for association reaction of lac repressor-operator [RO] complex

Range ~8.5 kcal/mole
Organism Bacteria Escherichia coli
Reference Riggs AD, Bourgeois S, Cohn M. The lac repressor-operator interaction. 3. Kinetic studies. J Mol Biol. 1970 Nov 1453(3):401-17 p.410 top paragraph & p.412 2nd paragraphPubMed ID4924006
Method Abstract p.401: "A sensitive membrane filter assay for the lac repressor-operator complex has been used to study the kinetics of repressor and operator interaction."
Comments P.410 top paragraph: "The rate of association as a function of temperature is shown as an Arrhenius plot in Figure 7. The reaction is relatively insensitive to temperature, however, significant changes were measured, the reaction being about four times slower at 1°C than at 24°C. From Figure 7, [investigators] calculate that the Arrhenius activation energy for the association reaction is around 8.5 kcal/mole." P.410 caption to figure 7: "Arrhenius plot of the association rate constant (ka) as a function of temperature: Complete experiments were done similar to those shown in Fig. 6, each being at a different temperature. Since Tris buffer changes pH with temperature, care was taken to adjust each BB buffer solution to pH 7.4 at the desired temperatures. For each experiment, the rate of association (ka) was calculated from the slope of a linear plot of the data." p.412 2nd paragraph: "From the change in equilibrium constant with temperature, ΔH for the binding reaction is + 8.5 kcal/mole." P.402 4th paragraph: "BB buffer contains: 0.01 M-magnesium acetate, 0.01 M-KCl, 10^-4 M-EDTA, 10^-4M-dithiothreitol, 5% dimethyl sulfoxide, 0.01 M-Tris-HCl, pH 7.4 at 24˚C, and 50 µg bovine serum albumin/ml."
Entered by Uri M
ID 114353