Table 1. Clamp loader structures previously obtained for the various states in the clamp loading cycle.

Clamp loader prior to clamp binding
Species	Composition	Reference	PDB accession number
E. coli	Clamp loader alone	Jeruzalmi et al., 2001a	1JR3
E. coli	Clamp loader, ADP	Kazmirski et al., 2004	1XXI
E. coli	Clamp loader, ATP analog	Kazmirski et al., 2004	1XXH
E. coli	Clamp loader, ATP analog, primer/template DNA	Simonetta et al., 2009	3GLF
Encounter complex of clamp loader bound to the closed clamp
H. sapiens	Clamp loader bound to the clamp, ATP analog	Gaubitz et al., 2020	6VVO
S. cerevisiae	Clamp loader bound to the closed clamp, ATP analog	Bowman et al., 2004	1SXJ
Clamp loader bound to the clamp and primer/template DNA
T4 phage	Clamp loader, open clamp, ATP analog, DNA	Kelch et al., 2011	3U60
T4 phage	Clamp loader, closed clamp, ATP analog, DNA	Kelch et al., 2011	3U5Z
T4 phage	Clamp loader, closed clamp, ATP analog, ADP, DNA	Kelch et al., 2011	3U61