A structural snapshot of the multiple working states of the Mpox virus helicase-primase D5.

The Mpox virus (or Monkeypox virus, MPXV) uses its own encoded proteins to form a replication machine that replicates the viral genome in the host cell cytoplasm, making this machinery a key target for antiviral drug design. The D5 (also known as the OPG117 or E5) protein, a bi-functional helicase-primase enzyme, is crucial in the MPXV replication machinery and genome uncoating process. Recently, cryo-electron microscopy (cryo-EM) structures of D5 in multiple states have been determined. These structures have elucidated the full trajectory of the MPXV D5 helicase-primase as it moves along single-stranded DNA, providing unprecedented advancements in the molecular dynamics and unwinding mechanism. This structural snapshot describes the structural features of the D5 protein and dissects the broader implications of its pivotal role in MPXV replication.