Figure 3.

Organization of eukaryotic MCM(2–7). Interactions between protomers of MCM result in a heterohexamer of defined geometry (Ishimi 1997; Schwacha and Bell 2001; Davey et al. 2003). In the cartoon, the Ks indicate the cis-acting Walker A lysine residue of a given subunit, and the Rs show the trans-acting arginine fingers. Thus, the active site between protomers is contributed to by the cis surface of one protomer and the trans surface of its neighbor. As detailed in the text, considerable biochemical and structural data support the existence of a gate between subunits Mcm2 and Mcm5 (right panel).