Fig. 5. Structure of the γ complex clamp loader.

(A) Schematic representation of the arrangement of the clamp loader subunits demonstrating the circular orientation of the five subunits. The pentameric circular assembly is interrupted by a gap between the δ and δ′ subunits, leaving space for the passage of DNA. The χ and ψ subunits are thought to attach to the γ subunit via ψ {Gao, 2001 #816} (B) Ribbon representation of the crystal structure of the minimal γ complex clamp loader γ₃δδ′). The Cterminal domains create a tight circular collar. The N-termini containing the two AAA⁺ domains are suspended downwards and adapt a conformation in which the δ and δ′ subunits create a gap large enough for the DNA to enter. The β clamp interacts with the N terminal domains.