Crystallographic closed ternary complex of polymerase beta (CPK) with primer/template DNA (ribbon) and ddCTP (yellow). Polymerase beta is composed with two subdomains (335 residues):lyase (8-kDa) and polymerase (31-kDa). Shape of the latter is like a hand: thumb, palm, and fingers, which is an overall architectural feature among most polymerases.
(For detailed information, see the article "Polymerase β Simulations Suggest That Arg258 Rotation is a Slow Step Rather Than Large Subdomain Motions Per Se", L. Yang, W. A. Beard, S. H. Wilson, S. Broyde, T. Schlick, J. Mol. Biol., 2002, 317:651-671).