DNA polymerase III (EC 2.7.7.7) is comprised of three tightly associated subunits, alpha, epsilon and theta. This family contains the theta subunit. The structure of the theta subunit shows that the N-terminal two thirds is comprised of three helices while the C-terminal third is disordered [1]. The function of the theta subunit is poorly understood, but the interaction of the theta subunit with the epsilon subunit is thought to enhance the 3' to 5' exonucleolytic proofreading activity of epsilon [2].

1: NMR solution structure of the theta subunit of DNA polymerase III from Escherichia coli. Keniry MA, Berthon HA, Yang JY, Miles CS, Dixon NE; Protein Sci 2000;9:721-733. PMID:10794414

2: Elucidation of the epsilon-theta subunit interface of Escherichia coli DNA polymerase III by NMR spectroscopy. DeRose EF, Darden T, Harvey S, Gabel S, Perrino FW, Schaaper RM, London RE; Biochemistry 2003;42:3635-3644. PMID:12667053