3J17

Structure of a transcribing cypovirus by cryo-electron microscopy

Summary for 3J17

• Entry DOI: 10.2210/pdb3j17/pdb
• EMDB information: 5376
• Descriptor: Structural protein VP3, VP1, Structural protein VP5 (3 entities in total)
• Functional Keywords: dsrna virus reoviridae transcribing cypovirus, virus
• Biological source: Bombyx mori cypovirus 1 (BmCPV); More
• Total number of polymer chains: 5
• Total formula weight: 517694.46

Authors

Yang, C.,Ji, G.,Liu, H.,Zhang, K.,Liu, G.,Sun, F.,Zhu, P.,Cheng, L. (deposition date: 2011-12-25, release date: 2012-04-04, Last modification date: 2025-03-26)

Primary citation

Yang, C.,Ji, G.,Liu, H.,Zhang, K.,Liu, G.,Sun, F.,Zhu, P.,Cheng, L.
Cryo-EM structure of a transcribing cypovirus.
Proc.Natl.Acad.Sci.USA, 109:6118-6123, 2012

PubMed Abstract: Double-stranded RNA viruses in the family Reoviridae are capable of transcribing and capping nascent mRNA within an icosahedral viral capsid that remains intact throughout repeated transcription cycles. However, how the highly coordinated mRNA transcription and capping process is facilitated by viral capsid proteins is still unknown. Cypovirus provides a good model system for studying the mRNA transcription and capping mechanism of viruses in the family Reoviridae. Here, we report a full backbone model of a transcribing cypovirus built from a near-atomic-resolution density map by cryoelectron microscopy. Compared with the structure of a nontranscribing cypovirus, the major capsid proteins of transcribing cypovirus undergo a series of conformational changes, giving rise to structural changes in the capsid shell: (i) an enlarged capsid chamber, which provides genomic RNA with more flexibility to move within the densely packed capsid, and (ii) a widened peripentonal channel in the capsid shell, which we confirmed to be a pathway for nascent mRNA. A rod-like structure attributable to a partially resolved nascent mRNA was observed in this channel. In addition, conformational change in the turret protein results in a relatively open turret at each fivefold axis. A GMP moiety, which is transferred to 5'-diphosphorylated mRNA during the mRNA capping reaction, was identified in the pocket-like guanylyltransferase domain of the turret protein.

PubMed: 22492979
DOI: 10.1073/pnas.1200206109

Experimental method

ELECTRON MICROSCOPY (4.1 Å)