Su, Xun-ChengJergic, SlobodanOzawa, KiyoshiBurns, NicolasDixon, NicholasOtting, Gottfried2015-12-070925-2738http://hdl.handle.net/1885/27995The use of 15N-relaxation data for determination of the dissociation constant of a protein-protein complex is proposed for the situation where a 15N-labeled protein is bound to an unlabeled protein of high molecular weight, and the chemical exchange between bound and free protein is fast on the NMR time scale. The approach is shown to be suitable for estimating dissociation constants in the micromolar to millimolar range, using protein solutions at relatively low concentration. An example is shown for the interaction between two subunits from the Escherichia coli DNA polymerase III complex, involving a 15N-labeled fragment of the C-terminal domain of the τ subunit (15 kDa) and the unlabeled α subunit (130 kDa).Keywords: bacterial DNA; DNA directed DNA polymerase gamma; nitrogen 15; protein subunit; article; carboxy terminal sequence; chemical interaction; concentration response; dissociation constant; Escherichia coli; isotope labeling; molecular weight; nitrogen nuclear 15N relaxation; Chemical exchange; Dissociation constant; E. coli DNA polymerase III; Protein-protein complex; Subunits a and t200710.1007/s10858-007-9147-92015-12-07