Fig. 3: A putative exit groove of lagging strand DNA between ZF domains of Mcm3 and 5.

a Close up of the DNA fork within the ZF regions, with the position of cryo-EM density loss of the lagging strand (dashed green curves) positioned toward the viewer. This density loss occurs at a groove between ZF domains of Mcm3 and 5. The floor of the groove is lined by a long hairpin loop (labeled by 1 and 2 inside red circles) of Mcm3 ZF domain, which has the unique and conserved feature among eukaryotic CMGs of lacking a Zn atom. A loop in the Mcm5 ZF domain (labeled by “3” in a red circle) forms the left wall of the groove and projects two Arg residues towards the putative lagging strand groove. b The gap between ZF domains of Mcm3 and 5 is sustained by the ordered N-terminal 14-residue peptide of the neighboring Mcm7, shown in cartoon and highlighted in red shade. This peptide forms the right wall of the groove. c Sequence alignment of the groove-forming loops of the ZF domains of Mcm3 and Mcm5. Sc: Saccharomyces cerevisiae, Dr: Danio rerio, Mm: Mus musculus, and Hs: Homo sapiens. Invariant residues are highlighted in green, identical residues in yellow, and similar residues in cyan.