<p> The <taxon tax_id="562">Escherichia coli</taxon> DNA polymerase III gamma complex clamp loader assembles the ring-shaped beta sliding clamp onto DNA. The core polymerase is tethered to the template by beta, enabling progressive replication of the genome. The E. coli complex clamp loader contains five different subunits, clamp loading only requires 3 of these - the gamma, delta, delta' complex. Three gamma subunits, and one each of delta and delta', are arranged in a circle. Each subunit adopts the same chain topology, and folds into three domains. However, the relative orientation of these domains is different for each subunit. The carboxy-terminal domains provide the major subunit contacts of the pentamer, although other intersubunit contacts are present. The amino-terminal domains do not form a continuous circle. These domains are arranged in a highly asymmetric fashion, and appear to dangle under the carboxy-terminal pentamer 'umbrella' [<cite idref="PUB00010612"/>].</p>