7et3
C5 portal vertex in the enveloped virion capsid
Structural highlights
FunctionSCP_HCMVA Participates in the assembly of the infectious particles by decorating the outer surface of the capsid shell and thus forming a layer between the capsid and the tegument. Complexes composed of the major capsid protein and small capsomere-interacting protein/SCP assemble together in the host cytoplasm and are translocated to the nucleus, where they accumulate and participate in capsid assembly. Publication Abstract from PubMedHow the human cytomegalovirus (HCMV) genome-the largest among human herpesviruses-is packaged, retained, and ejected remains unclear. We present the in situ structures of the symmetry-mismatched portal and the capsid vertex-specific components (CVSCs) of HCMV. The 5-fold symmetric 10-helix anchor-uncommon among known portals-contacts the portal-encircling DNA, which is presumed to squeeze the portal as the genome packaging proceeds. We surmise that the 10-helix anchor dampens this action to delay the portal reaching a "head-full" packaging state, thus facilitating the large genome to be packaged. The 6-fold symmetric turret, latched via a coiled coil to a helix from a major capsid protein, supports the portal to retain the packaged genome. CVSCs at the penton vertices-presumed to increase inner capsid pressure-display a low stoichiometry, which would aid genome retention. We also demonstrate that the portal and capsid undergo conformational changes to facilitate genome ejection after viral cell entry. Structural basis for genome packaging, retention, and ejection in human cytomegalovirus.,Li Z, Pang J, Dong L, Yu X Nat Commun. 2021 Jul 27;12(1):4538. doi: 10.1038/s41467-021-24820-3. PMID:34315863[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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