Members of this family, which are predominantly found in prokaryotic DNA polymerase III, assume an alpha helical structure, with a core of five alpha helices, and an additional small helix. They are essential for the formation of the polymerase clamp loader [1].

1: Crystal structure of the delta' subunit of the clamp-loader complex of E. coli DNA polymerase III. Guenther B, Onrust R, Sali A, O'Donnell M, Kuriyan J; Cell. 1997;91:335-345. PMID:9363942