9ZM2

Human cytomegalovirus UL52 4-mer

Summary for 9ZM2

• Entry DOI: 10.2210/pdb9zm2/pdb
• Related: 9ZLY
• EMDB information: 74419
• Descriptor: Packaging protein UL32 homolog, ZINC ION (2 entities in total)
• Functional Keywords: human cytomegalovirus, hcmv, viral genome packaging, packaging accessory factor, ul52, viral protein
• Biological source: Human betaherpesvirus 5
• Total number of polymer chains: 4
• Total formula weight: 297481.99

Authors

Bailey, E.J.,Devarkar, S.C.,Xiong, Y.,Didychuk, A.L. (deposition date: 2025-12-09, release date: 2026-07-01)

Primary citation

Bailey, E.J.,Devarkar, S.C.,Szczepaniak, R.,Meissner, L.M.,Chen, X.,Wu, C.,Weller, S.K.,Xiong, Y.,Didychuk, A.L.
Conserved assembly architecture of the essential herpesvirus packaging accessory factor.
Biorxiv, 2026

PubMed Abstract: To create a new wave of infectious virions, all herpesviruses require an accessory factor of unknown function to package their viral genomes into nascent capsids. Here, we present cryo-EM structures of the packaging accessory factor from the α-herpesvirus herpes simplex virus type 1 (HSV-1, UL32) and the β-herpesvirus human cytomegalovirus (HCMV, UL52). Unlike homologs from the γ-herpesviruses, neither UL32 nor UL52 form stable homopentameric rings. UL52 forms incomplete pentameric rings lacking one or two protomers. UL32 does not form stable higher-order species, but stabilization through chemical crosslinking revealed a novel quaternary structure where three pentameric rings assemble into a "tripentamer." Our results reveal that herpesvirus packaging accessory factors adopt distinct oligomeric states but are constrained to pentameric symmetry. Assembly of protomers into a ring creates a positively charged central channel that we show is critical for infectious virus production in HSV-1. Taken together, our study points to a structurally conserved, essential function of packaging accessory factors across the .

PubMed: 41648366
DOI: 10.64898/2026.01.22.701024

Experimental method

ELECTRON MICROSCOPY (3.29 Å)