The RecBCD complex interacts directly with the DNA sliding clamp in Escherichia coli.

DNA sliding clamps are central coordinators of genome replication and maintenance, yet the full binding network ("interactome") of the bacterial β-clamp remains incompletely defined. Here, we report a novel interaction between Escherichia coli β-clamp and the helicase-nuclease RecBCD complex. Using bacterial two-hybrid assays and co-immunoprecipitation, supported by fluorescence microscopy, we show that RecB associates with β-clamp. Nuclear magnetic resonance spectroscopy maps the interaction to the canonical ligand pocket of β-clamp and identifies a clamp-binding motif in RecB (residues 1018-1023, QVEMEF), whose mutation abolishes binding. Functional assays indicate that this interaction occurs upon conformational switching of RecBCD at a Chi site, and disruption of the motif reduces survival after DNA damage. We also find indications of a second binding site in the helicase domain of RecB. These findings expand the β-clamp interactome and suggest a previously unappreciated role for β-clamp in DNA double-strand break repair, with potential implications for antibacterial strategies.