dnaN

DnaN is the gene that encodes the beta sliding clamp subunit of bacterial DNA polymerase III. The beta clamp acts as a processivity factor, enabling the polymerase to synthesize long stretches of DNA without dissociating. The protein functions as a dimer, with each monomer contributing to a ring-shaped clamp that encircles double-stranded DNA.

The beta clamp is loaded onto primer-template DNA by a clamp loader in an ATP-dependent reaction, after which it tethers the DNA polymerase III core to DNA. Once loaded, the clamp remains associated with the polymerase, allowing rapid and processive DNA synthesis during replication. The clamp also serves as a docking platform for other proteins involved in replication and repair, coordinating activities such as lagging-strand synthesis, mismatch repair, and translesion synthesis through interactions with conserved binding motifs.

In terms of structure and conservation, the beta clamp is a highly conserved bacterial component and is typically around 40 kilodaltons per monomer, forming an 80- kilodalton dimer. Its role is essential for viability in most bacteria, making it a central part of the replication machinery. The dnaN gene is typically studied in the context of Escherichia coli and related bacteria, where it is part of the coordinated expression of replication factors.

DnaN is distinct from the eukaryotic PCNA sliding clamp, which serves a similar function in archaea and eukaryotes but is structurally different. See also: DNA polymerase III, sliding clamp, clamp loader, PCNA.

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