Structural highlights
Function
[CAPSD_BPQBE] Capsid protein self-assembles to form an icosahedral capsid with a T=3 symmetry, about 26 nm in diameter, and consisting of 89 capsid proteins dimers (178 capsid proteins) (PubMed:27671640, PubMed:19913556). Involved in viral genome encapsidation through the interaction between a capsid protein dimer and the multiple packaging signals present in the RNA genome (PubMed:8943226, PubMed:27671640). Binding of the capsid proteins to the viral RNA induces a conformational change required for efficient T=3 shell formation (PubMed:19913556). The capsid contains also 1 copy of the A2 maturation protein (PubMed:27671640).[1] [2] [3] Acts as a translational repressor of viral replicase synthesis late in infection. This latter function is the result of capsid protein interaction with an RNA hairpin which contains the replicase ribosome-binding site.[4]
Publication Abstract from PubMed
The coat proteins (CPs) of single-stranded RNA bacteriophages (ssRNA phages) directly assemble around the genomic RNA (gRNA) to form a near-icosahedral capsid with a single maturation protein (Mat) that binds the gRNA and interacts with the retractile pilus during infection of the host. Understanding the assembly of ssRNA phages is essential for their use in biotechnology, such as RNA protection and delivery. Here, we present the complete gRNA model of the ssRNA phage Qbeta, revealing that the 3' untranslated region binds to the Mat and the 4127 nucleotides fold domain-by-domain, and is connected through long-range RNA-RNA interactions, such as kissing loops. Thirty-three operator-like RNA stem-loops are located and primarily interact with the asymmetric A/B CP-dimers, suggesting a pathway for the assembly of the virions. Additionally, we have discovered various forms of the virus-like particles (VLPs), including the canonical T = 3 icosahedral, larger T = 4 icosahedral, prolate, oblate forms, and a small prolate form elongated along the 3-fold axis. These particles are all produced during a normal infection, as well as when overexpressing the CPs. When overexpressing the shorter RNA fragments encoding only the CPs, we observed an increased percentage of the smaller VLPs, which may be sufficient to encapsidate a shorter RNA.
Structural Assembly of Qbeta Virion and Its Diverse Forms of Virus-like Particles.,Chang JY, Gorzelnik KV, Thongchol J, Zhang J Viruses. 2022 Jan 24;14(2). pii: v14020225. doi: 10.3390/v14020225. PMID:35215818[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Basnak G, Morton VL, Rolfsson O, Stonehouse NJ, Ashcroft AE, Stockley PG. Viral genomic single-stranded RNA directs the pathway toward a T=3 capsid. J Mol Biol. 2010 Feb 5;395(5):924-36. doi: 10.1016/j.jmb.2009.11.018. Epub 2009, Nov 12. PMID:19913556 doi:http://dx.doi.org/10.1016/j.jmb.2009.11.018
- ↑ Gorzelnik KV, Cui Z, Reed CA, Jakana J, Young R, Zhang J. Asymmetric cryo-EM structure of the canonical Allolevivirus Qbeta reveals a single maturation protein and the genomic ssRNA in situ. Proc Natl Acad Sci U S A. 2016 Sep 26. pii: 201609482. PMID:27671640 doi:http://dx.doi.org/10.1073/pnas.1609482113
- ↑ Lim F, Spingola M, Peabody DS. The RNA-binding site of bacteriophage Qbeta coat protein. J Biol Chem. 1996 Dec 13;271(50):31839-45. PMID:8943226
- ↑ Lim F, Spingola M, Peabody DS. The RNA-binding site of bacteriophage Qbeta coat protein. J Biol Chem. 1996 Dec 13;271(50):31839-45. PMID:8943226
- ↑ Chang JY, Gorzelnik KV, Thongchol J, Zhang J. Structural Assembly of Qbeta Virion and Its Diverse Forms of Virus-like Particles. Viruses. 2022 Jan 24;14(2). pii: v14020225. doi: 10.3390/v14020225. PMID:35215818 doi:http://dx.doi.org/10.3390/v14020225
