T4 Bacteriophage clamp gp45

These are models of the closed and open forms of the T4 bacteriophage DNA clamp. The "open form" occurs when the clamp is being loaded onto DNA by a "clamp loader" complex.

"Enterobacteria phage T4 is a bacteriophage that infects Escherichia coli bacteria."
--http://en.wikipedia.org/wiki/Enterobacteria_phage_T4

"The viral gp45 sliding clamp subunit protein contains two domains. Each domain consists of two alpha helices and two beta sheets -? the fold is duplicated and has internal pseudo