NMR resonance assignments for the N-terminal domain of the δ subunit of the E. coli γ clamp loader complex.

The β-clamp protein and the γ clamp loader complex are essential components of bacterial DNA replication machinery. The β-clamp is a ring-shaped homodimer that encircles DNA and increases the efficiency of replication by providing a binding platform for DNA polymerases and other replication-related proteins. The β-clamp is loaded onto DNA by the five-subunit γ clamp loader complex in a multi-step ATP-dependent process. The initial steps of this process involve the cooperative binding of the β-clamp by the five subunits of ATP-bound clamp loader, which induces or traps an open conformation of the clamp. Remarkably, the δ subunit of the E. coli clamp loader, or even its 140 residue N-terminal domain (called mini-δ), alone can shift conformational equilibrium of the β-clamp towards the open state. Here we report nearly complete backbone and side-chain 1 H, 13 C and 15 N NMR resonance assignments of mini-δ that will facilitate NMR studies of the mechanisms of β-clamp opening and its loading on DNA by the clamp loader.