The assembly of Escherichia coli DNA polymerase III catalytic core

This study is mainly focused on the assembly of the DNA polymerase III catalytic core of Escherichia coli. This enzyme is responsible for the chromosome replication and it is constituted of multiple subunits. In particular, the polymerase and the exonuclease (proofreading) activities are located into two different subunits: (coded by dnaE gene) and , (coded by dnaQ). The catalytic core is composed also of the subunit with an accessory role and a dispensable nature. On the contrary, the dnaE and dnaQ are essential genes and their interaction is crucial for the assembly of a DNA polymerase III active enzyme. Several data are available on the properties of the DNA polymerase III in vitro, while little information concerns the assembly in vivo of this enzyme. The present work investigated the interaction of alpha and epsilon subunits by using different truncated forms produced in vivo, in order to identify which residues of epsilon (DnaQ) are essential for binding to alpha. Moreover, the stability of the mutant proteins was analyzed and we found that the C-terminal region of epsilon is labile and affected by proteolysis. In addition, different factors (proteases and chaperones) potentially involved in the regulation of epsilon stability have been studied.