Download MendeleyThe E. coli DnaX clamp loader sharply bends DNA to load beta-clamp at nicks and small gaps.
Zheng, F., Yao, N.Y., Georgescu, R.E., Lyu, M., O'Donnell, M.E., Li, H.(2026) Mol Cell 86: 2055-2069.e10
- PubMed: 42140189 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1016/j.molcel.2026.04.020
- Primary Citation Related Structures:
9OYB, 9OYC, 9OYD, 9OYE, 9OYF, 9OYG, 9OYH, 9OYI, 9OYJ, 9OYK, 9OYL, 9OYM, 9OYN - PubMed Abstract:
DNA sliding clamps are essential for processive DNA synthesis in all domains of life and are loaded by ATP-dependent clamp loaders that recognize recessed 3' ends. How clamp loaders function at nicks and small single-stranded DNA (ssDNA) gaps-common DNA repair intermediates-remains unclear. Here, we show that the bacterial E. coli DnaX clamp loader uses a mechanism distinct from its eukaryotic counterpart. Whereas eukaryotic replication factor C (RFC) unwinds DNA at the recessed 3' end and stabilizes the 5'-dsDNA (double-stranded DNA) at a shoulder site, the bacterial DnaX-complex neither unwinds DNA nor stably binds the 5'-dsDNA in vitro. Instead, cryo-EM structures reveal that the β-clamp contains a conserved external DNA-binding site that bends gapped DNA by ∼150°, promoting insertion of 3'-dsDNA into the clamp. This DNA-bending mechanism enables efficient β-clamp loading at nicks and small gaps and reveals a distinct bacterial strategy likely important for DNA repair.
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
Organizational Affiliation:
