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

The interaction between two physiological redox partners, trimethylami ne dehydrogenase and electron-transferring flavoprotein, has been char acterized quantitatively by analytical ultracentrifugation at 4 degree s C, Analysis of sedimentation-equilibrium distributions obtained at 1 5 000 rpm for mixtures in 10 mM potassium phosphate, pH 7.5, by means of the psi function [Wills: P. R. Jacobsen, M. P. & Winter, D. J. (199 6) Biopolymers 38, 119-130] has yielded an intrinsic dissociation cons tant of 3-7 mu M for the interaction of electron-transferring flavopro tein with two equivalent and independent sites on the homodimeric enzy me. This investigation indicates the potential of sedimentation equili brium for the quantitative characterization of interactions between di ssimilar macromolecules.