An Ultracentrifugal Approach to Quantitative Characterization of the Molecular Assembly of a Physiological Electron‐Transfer Complex. The Interaction of Electron‐Transferring Flavoprotein with Trimethylamine Dehydrogenase

Abstract
The interaction between two physiological redox partners, trimethylamine dehydrogenase and electron-transferring flavoprotein, has been characterized quantitatively by analytical ultracentrifugation at 4°C. Analysis of sedimentation-equilibrium distributions obtained at 15000 rpm for mixtures in 10 mM potassium phosphate, pH 7.5, by means of the psi function [Wills, P. R., Jacobsen, M. P. & Winzor, D. J. (1996) Biopolymers 38, 119–1301 has yielded an intrinsic dissociation constant of 3–7 μM for the interaction of electron-transferring flavoprotein with two equivalent and independent sites on the homodimeric enzyme. This investigation indicates the potential of sedimentation equilibrium for the quantitative characterization of interactions between dissimilar macromolecules.