Analysis of the crystal structure of an active MCM hexamer

• DOI: 10.7554/elife.03433
• Publication Date: 2014-09-26T09:33:37Z
• Authors: Justin M Miller; Buenafe T Arachea; Leslie B Epling; Eric J Enemark
• Keywords: Models, Molecular; 0301 basic medicine; archaea; QH301-705.5; Science; Recombinant Fusion Proteins; Molecular Sequence Data; DNA replication; Crystallography, X-Ray; Biochemistry; 03 medical and health sciences; Allosteric Regulation; Catalytic Domain; Amino Acid Sequence; Biology (General); crystallography; Adenosine Triphosphatases; Minichromosome Maintenance Proteins; Q; R; MCM; Protein Structure, Tertiary; Adenosine Diphosphate; Pyrococcus furiosus; helicase; Sulfolobus solfataricus; Medicine; Protein Multimerization

In a previous Research article (<xref ref-type="bibr" rid="bib25">Froelich et al., 2014</xref>), we suggested an MCM helicase activation mechanism, but were limited in discussing the ATPase domain because it was absent from the crystal structure. Here we present the crystal structure of a nearly full-length MCM hexamer that is helicase-active and thus has all features essential for unwinding DNA. The structure is a chimera of Sulfolobus solfataricus N-terminal domain and Pyrococcus furiosus ATPase domain. We discuss three major findings: 1) a novel conformation for the A-subdomain that could play a role in MCM regulation; 2) interaction of a universally conserved glutamine in the N-terminal Allosteric Communication Loop with the AAA+ domain helix-2-insert (h2i); and 3) a recessed binding pocket for the MCM ssDNA-binding motif influenced by the h2i. We suggest that during helicase activation, the h2i clamps down on the leading strand to facilitate strand retention and regulate ATP hydrolysis.