9K3A

Cyanophage A4 pre-ejectosome with C1 symmetry

Summary for 9K3A

• Entry DOI: 10.2210/pdb9k3a/pdb
• EMDB information: 62011
• Descriptor: Tail protein (2 entities in total)
• Functional Keywords: cyanophage, virus, capsid, viral protein
• Biological source: Anabaena phage A-4L; More
• Total number of polymer chains: 2
• Total formula weight: 315710.29

Authors

Hou, P.,Li, Q.,Zhou, C.Z. (deposition date: 2024-10-18, release date: 2025-04-09, Last modification date: 2025-06-18)

Primary citation

Hou, P.,Zhou, R.Q.,Jiang, Y.L.,Yu, R.C.,Du, K.,Gan, N.,Ke, F.,Zhang, Q.Y.,Li, Q.,Zhou, C.Z.
Cryo-EM structure of cyanopodophage A4 reveals a pentameric pre-ejectosome in the double-stabilized capsid.
Proc.Natl.Acad.Sci.USA, 122:e2423403122-e2423403122, 2025

PubMed Abstract: Upon infection, the podophages usually eject a couple of proteins from the capsid to form a transmembrane ejectosome on the host cell membrane that facilitates the ejection of viral genome. However, it remains unclear how these proteins of pre-ejectosome are finely assembled at the center of highly packaged genome. Here, we report the intact structure of cyanopodophage A4, which consists of a capsid stabilized by two types of cement proteins and a short tail attached with six tail fibers. Notably, we find a pentameric pre-ejectosome at the core of capsid, which is composed of four ejection proteins wrapped into a coaxial cylinder of triple layers. Moreover, a segment of genomic DNA runs along the positively charged circular cleft formed by two ejection proteins. Based on the mortise-and-tenon architecture of pre-ejectosome in combination with previous studies, we propose a putative DNA packaging process and ejection mechanism for podophages. These findings largely enrich our knowledge on the assembly mechanism of podophages, which might facilitate the application of A4 as a chassis cyanophage in synthetic biology.

PubMed: 40163721
DOI: 10.1073/pnas.2423403122

Experimental method

ELECTRON MICROSCOPY (3.6 Å)