PT  - JOURNAL ARTICLE
AU  - Anuska Das
AU  - Jay Rai
AU  - Mitchell O. Roth
AU  - Yuerong Shu
AU  - Megan L. Medina
AU  - MacKenzie R. Barakat
AU  - Hong Li
TI  - Conformational Changes Regulate Metal Coordination in the Catalytic Sites of Cas9
AID  - 10.1101/2022.09.10.507422
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.09.10.507422
4099  - http://biorxiv.org/content/early/2022/09/11/2022.09.10.507422.short
4100  - http://biorxiv.org/content/early/2022/09/11/2022.09.10.507422.full
AB  - The control of CRISPR-Cas9 activities plays an essential role in its safe adoption for clinical and research applications. Previous studies have identified conformational dynamics of Cas9 as a key regulatory element for its enzymatic activity. The molecular basis for how conformations influence the catalytic processes at both nuclease domains, however, remains elusive. Here we present well-resolved cryo-EM structures of the active Acidothermus cellulolyticus Cas9 (AceCas9) complexes representing pre-cleavage (2.9 Å), two reaction intermediate (2.2 Å and 2.4 Å) and two post-cleavage (2.6 Å and 2.7 Å) states that reveal active site rearrangement during DNA binding and phosphodiester bond breakage by Cas9. Strikingly, large domain rearrangements in Cas9 triggered by the cognate DNA result in subtle changes in active sites that facilitate coordination of metal ions required for catalysis. The two reaction intermediate structures further reveal small oscillations in domain conformations, which alternates the reactive states of the two catalytic centers, thereby coupling cleavage of the two DNA strands. Consistent with the roles of conformations in organizing the active sites, adjustments of metal coordination ligands lead to altered metal specificity.Competing Interest StatementThe authors have declared no competing interest.