| Structural highlights
Function
CAPSD_BPHK7 Assembles to form an icosahedral capsid of 66 nm, with a T=7 laevo symmetry (PubMed:11000116, PubMed:21276801). Responsible for its self-assembly into a procapsid. The phage does not need to encode a separate scaffolfing protein because its capsid protein contains the delta domain that carries that function.[1] [2] [3] [4]
Publication Abstract from PubMed
Double-stranded DNA viruses utilise machinery, made of terminase proteins, to package viral DNA into the capsid. For cos bacteriophage, a defined signal, recognised by small terminase, flanks each genome unit. Here we present the first structural data for a cos virus DNA packaging motor, assembled from the bacteriophage HK97 terminase proteins, procapsids encompassing the portal protein, and DNA containing a cos site. The cryo-EM structure is consistent with the packaging termination state adopted after DNA cleavage, with DNA density within the large terminase assembly ending abruptly at the portal protein entrance. Retention of the large terminase complex after cleavage of the short DNA substrate suggests that motor dissociation from the capsid requires headful pressure, in common with pac viruses. Interestingly, the clip domain of the 12-subunit portal protein does not adhere to C12 symmetry, indicating asymmetry induced by binding of the large terminase/DNA. The motor assembly is also highly asymmetric, showing a ring of 5 large terminase monomers, tilted against the portal. Variable degrees of extension between N- and C-terminal domains of individual subunits suggest a mechanism of DNA translocation driven by inter-domain contraction and relaxation.
Insights into a viral motor: the structure of the HK97 packaging termination assembly.,Hawkins DEDP, Bayfield OW, Fung HKH, Grba DN, Huet A, Conway JF, Antson AA Nucleic Acids Res. 2023 Jul 21;51(13):7025-7035. doi: 10.1093/nar/gkad480. PMID:37293963[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Wikoff WR, Liljas L, Duda RL, Tsuruta H, Hendrix RW, Johnson JE. Topologically linked protein rings in the bacteriophage HK97 capsid. Science. 2000 Sep 22;289(5487):2129-33. PMID:11000116
- ↑ Huang RK, Khayat R, Lee KK, Gertsman I, Duda RL, Hendrix RW, Johnson JE. The Prohead-I Structure of Bacteriophage HK97: Implications for Scaffold-Mediated Control of Particle Assembly and Maturation. J Mol Biol. 2011 Jan 27. PMID:21276801 doi:10.1016/j.jmb.2011.01.016
- ↑ Duda RL, Martincic K, Xie Z, Hendrix RW. Bacteriophage HK97 head assembly. FEMS Microbiol Rev. 1995 Aug;17(1-2):41-6. PMID:7669350 doi:10.1111/j.1574-6976.1995.tb00186.x
- ↑ Duda RL, Martincic K, Hendrix RW. Genetic basis of bacteriophage HK97 prohead assembly. J Mol Biol. 1995 Apr 7;247(4):636-47. PMID:7723020 doi:10.1006/jmbi.1994.0169
- ↑ Hawkins DEDP, Bayfield OW, Fung HKH, Grba DN, Huet A, Conway JF, Antson AA. Insights into a viral motor: the structure of the HK97 packaging termination assembly. Nucleic Acids Res. 2023 Jul 21;51(13):7025-7035. PMID:37293963 doi:10.1093/nar/gkad480
|
