Abstract
REDOR-based experiments with simultaneous (1)H-(13)C and (1)H-(15)N dipolar dephasing are explored for investigating intermolecular protein-protein interfaces in complexes formed by a U-(13)C,(15)N-labeled protein and its natural abundance binding partner. The application of a double-REDOR filter (dREDOR) results in a complete dephasing of proton magnetization in the U-(13)C,(15)N-enriched molecule while the proton magnetization of the unlabeled binding partner is not dephased. This retained proton magnetization is then transferred across the intermolecular interface by (1)H-(13)C or (1)H-(15)N cross polarization, permitting to establish the residues of the U-(13)C,(15)N-labeled protein, which constitute the binding interface. To assign the interface residues, this dREDOR-CPMAS element is incorporated as a building block into (13)C-(13)C correlation experiments. We established the validity of this approach on U-(13)C,(15)N-histidine and on a structurally characterized complex of dynactin's U-(13)C,(15)N-CAP-Gly domain with end-binding protein 1 (EB1). The approach introduced here is broadly applicable to the analysis of intermolecular interfaces when one of the binding partners in a complex cannot be isotopically labeled.