D. Jeruzalmi et al., Crystal structure of the processivity clamp loader gamma (gamma) complex of E-coli DNA polymerase III, CELL, 106(4), 2001, pp. 429-441
The gamma complex, an AAA+ ATPase, is the bacterial homolog of eukaryotic r
eplication factor C (RFC) that loads the sliding clamp (beta, homologous to
PCNA) onto DNA. The 2.7/3.0 Angstrom crystal structure of gamma complex re
veals a pentameric arrangement of subunits, with stoichiometry delta':gamma
(3):delta. The C-terminal domains of the subunits form a circular collar t
hat supports an asymmetric arrangement of the N-terminal ATP binding domain
s of the gamma motor and the structurally related domains of the delta' sta
tor and the delta wrench. The structure suggests a mechanism by which the g
amma complex switches between a closed state, in which the beta -interactin
g element of delta is hidden by delta', and an open form similar to the cry
stal structure, in which delta is free to bind to beta.