3zx8 | pdb_00003zx8
Cryo-EM reconstruction of native and expanded Turnip Crinkle virus
Structural highlights
Function[CAPSD_TCV] Capsid protein self-assembles to form an icosahedral capsid with a T=3 symmetry, about 32-35 nm in diameter, and consisting of 180 capsid proteins. Also acts as a suppressor of RNA-mediated gene silencing, also known as post-transcriptional gene silencing (PTGS), a mechanism of plant viral defense that limits the accumulation of viral RNAs.[1] [2] [3] Publication Abstract from PubMedWe have determined the three-dimensional structures of both native and expanded forms of turnip crinkle virus (TCV), using cryo-electron microscopy, which allows direct visualization of the encapsidated single-stranded RNA and coat protein (CP) N-terminal regions not seen in the high-resolution X-ray structure of the virion. The expanded form, which is a putative disassembly intermediate during infection, arises from a separation of the capsid-forming domains of the CP subunits. Capsid expansion leads to the formation of pores that could allow exit of the viral RNA. A subset of the CP N-terminal regions becomes proteolytically accessible in the expanded form, although the RNA remains inaccessible to nuclease. Sedimentation velocity assays suggest that the expanded state is metastable and that expansion is not fully reversible. Proteolytically cleaved CP subunits dissociate from the capsid, presumably leading to increased electrostatic repulsion within the viral RNA. Consistent with this idea, electron microscopy images show that proteolysis introduces asymmetry into the TCV capsid and allows initial extrusion of the genome from a defined site. The apparent formation of polysomes in wheat germ extracts suggests that subsequent uncoating is linked to translation. The implication is that the viral RNA and its capsid play multiple roles during primary infections, consistent with ribosome-mediated genome uncoating to avoid host antiviral activity. Isolation of an asymmetric RNA uncoating intermediate for a single-stranded RNA plant virus.,Bakker SE, Ford RJ, Barker AM, Robottom J, Saunders K, Pearson AR, Ranson NA, Stockley PG J Mol Biol. 2012 Mar 16;417(1-2):65-78. Epub 2012 Jan 27. PMID:22306464[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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