Extended Data Fig. 6: Structure of ORC–DNA in different states.
From: Mechanism of head-to-head MCM double-hexamer formation revealed by cryo-EM
a–c, Comparison between the cross-linked ORC–DNA complex imaged in isolation (a), ORC–DNA in the OCCM complex (b) and ORC–DNA in the MO complex (c). Nucleotide occupancy appears the same in all three cases. It should be noted, however, that ORC–DNA alone and within the OCCM complex were co-incubated with ATPγS, whereas ORC in MO was imaged in ATP. Orc2 in ORC–DNA contains a visible winged-helix domain (WHD) that topologically closes ORC around DNA. ORC in OCCM is Cdc6-engaged. The Orc2 winged-helix domain is virtually absent in the cryo-EM map of the MO, which indicates that this domain is flexible. This discrepancy might reflect a different ORC configuration in MO, or the fact that the previously published ORC–DNA structure was stabilized by glutaraldehyde crosslinking. Despite Cdc6 being present in the sample, ORC in MO is not Cdc6-bound.
