Related to Fig. 6 ; hydrophobic interactions between human MCM subunits. 6.77 Å resolution cryo-EM structure of the human MCM2/4/6 protein complex (PDB code 6XTY). Structural analyses were performed using ChimeraX (ver 1.8, https://www.cgl.ucsf.edu/chimerax/download.html) (Meng et al., 2023). (A) Interface between human MCM2 and MCM6 subunits. The structure of MCM2 is shown as a ribbon diagram and that of MCM6 is shown as a 3D density map with colored hydrophobicity surfaces. The zoomed view shows the hydrophobic patches on the surface of MCM6 that are covered by MCM2. (B) The interface between human MCM4 and MCM6 subunits. The structure of MCM4 is shown as a ribbon diagram and that of MCM6 as a 3D density map. The zoomed view shows the hydrophobic patches on the surface of MCM6 that are covered by MCM4. (C) Similar to the reported association between yeast MCM4 and MCM6, the hydrophobic interactions between Phe³⁴⁶ of human MCM4 and Ile¹³¹ of human MCM6 (which correspond to Phe³⁹¹ of yeast MCM4 and Ile²⁸⁴ of yeast MCM6, respectively) are critical for driving this subunit–subunit interaction.