5vf3 | pdb_00005vf3
Bacteriophage T4 isometric capsid
Structural highlights
Function[HOC_BPT4] Component of T4 head. Interacts with the major capsid protein and thus may exert an indirect effect on capsid stability. [CAPSP_BPT4] Capsid protein that self-associates to form 11 pentons, building the T=13 laevo capsid in association with 160 hexamers of gp23* and one dodecamer of gp20.[1] [2] [CAPSH_BPT4] Major capsid protein that self-associates to form 160 hexamers, building most of the T=13 laevo capsid in association with 11 pentons made of gp24 and one dodecamer of gp20. Folding of gp23 requires the assistance of two chaperones, the host chaperone groL acting with the phage encoded gp23-specific chaperone, gp31. The capsid also contains two nonessential outer capsid proteins, Hoc and Soc, which decorate the capsid surface. Through binding to adjacent gp23 subunits, Soc reinforces the capsid structure.[3] [4] Publication Abstract from PubMedThe 3.3-A cryo-EM structure of the 860-A-diameter isometric mutant bacteriophage T4 capsid has been determined. WT T4 has a prolate capsid characterized by triangulation numbers (T numbers) Tend = 13 for end caps and Tmid = 20 for midsection. A mutation in the major capsid protein, gp23, produced T=13 icosahedral capsids. The capsid is stabilized by 660 copies of the outer capsid protein, Soc, which clamp adjacent gp23 hexamers. The occupancies of Soc molecules are proportional to the size of the angle between the planes of adjacent hexameric capsomers. The angle between adjacent hexameric capsomers is greatest around the fivefold vertices, where there is the largest deviation from a planar hexagonal array. Thus, the Soc molecules reinforce the structure where there is the greatest strain in the gp23 hexagonal lattice. Mutations that change the angles between adjacent capsomers affect the positions of the pentameric vertices, resulting in different triangulation numbers in bacteriophage T4. The analysis of the T4 mutant head assembly gives guidance to how other icosahedral viruses reproducibly assemble into capsids with a predetermined T number, although the influence of scaffolding proteins is also important. Cryo-EM structure of the bacteriophage T4 isometric head at 3.3-A resolution and its relevance to the assembly of icosahedral viruses.,Chen Z, Sun L, Zhang Z, Fokine A, Padilla-Sanchez V, Hanein D, Jiang W, Rossmann MG, Rao VB Proc Natl Acad Sci U S A. 2017 Sep 11. pii: 201708483. doi:, 10.1073/pnas.1708483114. PMID:28893988[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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