Figure 2.
Binding of SecB to SecA. Wild-type SecA was loaded into the cell at a concentration of 5 μM dimer in 10 mM HEPES-KOH, 300 mM KOAc, 5 mM Mg(OAc)2, 2 mM TCEP (pH 7.6). Wild-type SecB (held in the syringe at 200 μM tetramer) in the same buffer was added in a sequence of 14 injections of 10 μL each after a first injection of 2 μL, which is included to expel any air that might be in the tip of the syringe. The heat of the first injection is not included in the analysis. (Upper) Raw data. (Lower) Integrated area of heat as a function of the molar ratio of the reactants. The points are the experimental data and the solid line is the calculated best fit.