Structural and functional characterization of P1L, an anti-apoptotic Bcl-2-like protein from monkeypox virus.

Mpox, caused by monkeypox virus (MPXV), remains a global public-health threat, with limited vaccine options and few mechanism-based therapeutics. MPXV P1L, a Bcl-2 like immune-evasion protein, suppresses antiviral signaling and regulates apoptosis, whereas its structural basis keeps unknown. Here we report the crystal structures of P1L and its mutant D14 N at 2.4 Å and 2.9 Å resolution, respectively. P1L forms a homodimer stabilized by a salt-bridge network at the dimer interface, notably involving Asp14 and Arg7. Mutation D14 N disrupts the dimeric interface. Structural comparison with cellular antiapoptotic Bcl-2 protein reveals a conserved groove characteristic of BH3-ligand binding, consistent with evolutionary mimicry of host regulatory motifs. Functionally, P1L protects cells from TNFα-induced apoptosis and interacts with the BH3-only protein BID, linking the conserved groove to apoptosis blockade. These findings identify P1L as a viral immune-evasion factor and provide a structural framework for discovering groove-targeting inhibitors with potential anti-poxvirus activity.