6uzc
From Proteopedia
Portal vertex structure of bacteriophage T4
Structural highlights
Function[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.[1] [2] [PORTL_BPT4] Forms the portal vertex of the capsid (PubMed:2685327, PubMed:24126213). This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection. The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel. Binds to the terminase subunits to form the packaging machine. Attaches to the host inner membrane most likely through interaction with host yidC and forms together with chaperone gp40 an initiator complex to form the prohead.[3] [4] Publication Abstract from PubMedLarge biological structures are assembled from smaller, often symmetric, sub-structures. However, asymmetry among sub-structures is fundamentally important for biological function. An extreme form of asymmetry, a 12-fold-symmetric dodecameric portal complex inserted into a 5-fold-symmetric capsid vertex, is found in numerous icosahedral viruses, including tailed bacteriophages, herpesviruses, and archaeal viruses. This vertex is critical for driving capsid assembly, DNA packaging, tail attachment, and genome ejection. Here, we report the near-atomic in situ structure of the symmetry-mismatched portal vertex from bacteriophage T4. Remarkably, the local structure of portal morphs to compensate for symmetry-mismatch, forming similar interactions in different capsid environments while maintaining strict symmetry in the rest of the structure. This creates a unique and unusually dynamic symmetry-mismatched vertex that is central to building an infectious virion. Structural morphing in a symmetry-mismatched viral vertex.,Fang Q, Tang WC, Tao P, Mahalingam M, Fokine A, Rossmann MG, Rao VB Nat Commun. 2020 Apr 6;11(1):1713. doi: 10.1038/s41467-020-15575-4. PMID:32249784[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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