Overview of EXT-hp mutations. A) Sequence alignments of MCMs across archaea (top) and eukaryotes (bottom), for the short region corresponding to the EXT-hp. Sso: Sulfolobus solfataricus. Sac: Sulfolobus acidocaldarius. Prn: Aeropyrum pernix. Mth: Methanothermobacter thermautotrophicus. Pyf: Pyrococcus furiosus. Tap: Thermoplasma acidophilum. Sp: Schizosaccharomyces pombe. Sc: Saccharomyces cerevisiae. Hs: Homo sapiens. Xl: Xenopus laevis. Dm: Drosophila melanogaster. At: Arabidopsis thaliana. B) Table of mutations used for this work. C) Tilted side view of the ssoMCM hexamer model, showing the EXT-hp on the external side of the hexamer and near the side channel. A single subunit is shown in cyan, with its EXT-hp in red. The ATP binding pocket and side-channel are indicated. D) Close up view of EXT-hp. Inside and outside refer to towards the central channel and away from the central channel, respectively. The locations of the residues mutated in this study are colored on the EXT-hp according to amino acid type, as in panel B.