Structural biology of Rad50 ATPase: ATP-driven conformational control in DNA double-strand break repair and the ABC-ATPase superfamily

To clarify the key role of Rad50 in DNA double-strand break repair (DSBR), we biochemically and structurally characterized ATP-bound and ATP-free Rad5 0 catalytic domain (Rad50cd) from Pyrococcus furiosus. Rad50cd displays ATP ase activity plus ATP-controlled dimerization and DNA binding activities. R ad50cd crystal structures identify probable protein and DNA interfaces and reveal an ABC-ATPase fold, linking Rad50 molecular mechanisms to ABC transp orters, including P glycoprotein and cystic fibrosis transmembrane conducta nce regulator. Binding of ATP gamma-phosphates to conserved signature motif s in two opposing Rad50cd molecules promotes dimerization that likely coupl es ATP hydrolysis to dimer dissociation and DNA release. These results, val idated by mutations, suggest unified molecular mechanisms for ATP-driven co operativity and allosteric control of ABC-ATPases in DSBR, membrane transpo rt, and chromosome condensation by SMC proteins.