Quantitative Analysis of Binding Protein-mediated ABC Transport Systems

We present a mathematical proof for the applicability of the Michaelis–Menten theory to the analysis of binding protein-dependent transport systems. Fitting the rate equation for transport of substrate to experimental data obtained with theEscherichia colimaltose system under conditions where the concentrations of the binding protein was varied, it was possible to determine without any further assumptions: (1)K1, the affinity constant of the binding protein towards its substrate; (2)K3, the affinity constant of the unloaded binding protein towards the membrane components; and (3)R, the concentration of the membrane component. This analysis allows determination of the alteration ofKMandVmaxof the system at varying concentrations of binding protein.