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C2 reconstruction of the concave tetramer in the cube-like assembly of 201Phi2-1 gp105
Structural highlights
FunctionCHMA_BP201 Self-assembles to forms a proteinaceous shell that encloses the viral DNA and compartmentalizes proteins and DNA during viral infection (PubMed:28082593, PubMed:28813669, PubMed:35922510). This micrometer-scale compartment contains narrow pores and is the site of viral replication, with the proteins involved in DNA replication localized inside (PubMed:28082593, PubMed:28813669, PubMed:35922510). Provides a surface for docking of capsids during packaging (PubMed:28082593, PubMed:28813669). Probably protects the viral genome against host defenses (Probable).[1] [2] [3] [4] Publication Abstract from PubMedThe jumbo phages encode proteins that assemble to form a nucleus-like compartment in infected cells. Here we report the cryo-EM structure and biochemistry characterization of gp105, a protein that is encoded by the jumbo phage 201phi2-1 and is involved in the formation of the nucleus-like compartment in phage 201phi2-1 infected Pseudomonas chlororaphis. We found that, although most gp105 molecules are in the monomeric state in solution, a small portion of gp105 assemble to form large sheet-like assemblies and small cube-like particles. Reconstruction of the cube-like particles showed that the particle consists of six flat head-to-tail tetramers arranged into an octahedral cube. The four molecules at the contact interface of two head-to-tail tetramers are 2-fold symmetry-related and constitute a concave tetramer. Further reconstructions without applying symmetry showed that molecules in the particles around the distal ends of a 3-fold axis are highly dynamic and have the tendency to open up the assembly. Local classifications and refinements of the concave tetramers in the cube-like particle resulted in a map of the concave tetramer at a resolution of 4.09 A. Structural analysis of the concave tetramer indicates that the N and C terminal fragments of gp105 are important for mediating the intermolecular interactions, which was further confirmed by mutagenesis studies. Biochemistry assays showed that, in solution, the cube-like particles of gp105 are liable to either disassemble to form the monomers or recruit more molecules to form the high molecular weight lattice-like assembly. We also found that monomeric gp105s can self-assemble to form large sheet-like assemblies in vitro, and the assembly of gp105 in vitro is a reversible dynamic process and temperature-dependent. Taken together, our results revealed the dynamic assembly of gp105, which helps to understand the development and function of the nucleus-like compartment assembled by phage-encoded proteins. Structural studies of the nucleus-like assembly of jumbo bacteriophage 201phi2-1.,Liu Z, Xiang Y Front Microbiol. 2023 Apr 17;14:1170112. doi: 10.3389/fmicb.2023.1170112. , eCollection 2023. PMID:37138628[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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