Structures of T=1 and T=3 Particles of Cucumber Necrosis Virus: Evidence of Internal Scaffolding

Katpally, Umesh; Kakani, Kishore; Reade, Ron; Dryden, Kelly A.; Rochon, D’Ann; Smith, Thomas J.

doi:10.1016/j.jmb.2006.09.060

Cited by 24 publications

(47 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Beneath the layer of RNA, surprisingly, is a second shell of protein (radius, 50 to 80 Å) that does not contain RNA. This neutron-scattering model agrees exceedingly well with the internal features observed in the CNV image reconstruction (7). It is tempting to speculate that the effects of some of the R-and arm-domain mutations on assembly (6, 10) are due to their participation in these internal structures.…”

supporting

confidence: 71%

“…The cryo-transmission electron microscopy structures of both the Tϭ1 and Tϭ3 particles have been determined (7). As expected, the structure of the Tϭ3 particles resembles the known structure of TBSV (5).…”

supporting

confidence: 56%

“…Recent studies have started to dissect the roles of the various capsid protein domains in the assembly of CNV particles (6,7). The internal disordered R domain appears to play a major role in particle formation that cannot be simply ascribed to neutralization of the negative charge of the RNA core by the addition of basic residues (6).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

Kakani

Katpally

et al. 2013

J Virol

Self Cite

View full text Add to dashboard Cite

Cucumber necrosis virus (CNV) is a member of the genus Tombusvirus and has a monopartite positive-sense RNA genome packaged in a T‫3؍‬ icosahedral particle. CNV is transmitted in nature via zoospores of the fungus Olpidium bornovanus. CNV undergoes a conformational change upon binding to the zoospore that is required for transmission, and specific polysaccharides on the zoospore surface have been implicated in binding. To better understand this transmission process, we have determined the atomic structure of CNV. As expected, being a member of the Tombusvirus genus, the core structure of CNV is highly similar to that of Tomato bushy stunt virus (TBSV), with major differences lying on the exposed loops. Also, as was seen with TBSV, CNV appears to have a calcium binding site between the subunits around the quasi-3-fold axes. However, unlike TBSV, there appears to be a novel zinc binding site within the ␤ annulus formed by the N termini of the three C subunits at the icosahedral 3-fold axes. Two of the mutations causing defective transmission map immediately around this zinc binding site. The other mutations causing defective transmission and particle formation are mapped onto the CNV structure, and it is likely that a number of the mutations affect zoospore transmission by affecting conformational transitions rather than directly affecting receptor binding. C ucumber necrosis virus (CNV) is a member of the genusTombusvirus and has a monopartite positive-sense RNA genome (1, 2). CNV is transmitted in nature via zoospores of the fungus Olpidium bornovanus (2-4). The type species of the Tombusvirus genus is Tomato bushy stunt virus (TBSV), and the structure of TBSV was the first virus structure determined by X-ray crystallography (5).These viruses have a Tϭ3 icosahedral protein shell with a diameter of ϳ300 Å formed from 180 identical coat protein (CP) subunits. The three conformationally distinct copies of the CPs, called A, B, and C, are shown in Fig. 1. The C subunits lie next to the icosahedral 2-fold axes, while the A and B subunits surround the 5-fold axes. Each capsid protein is comprised of three domains: the first ϳ60 residues at the N-terminal region (R), the shell (S) domain, and the protruding (P) domain (Fig. 2A). The first ϳ90 residues are disordered in the A and B subunits, while the first ϳ60 residues are disordered in the C subunit. Residues ϳ60 to 78 in the C subunit form a structure called the ␤ annulus that is thought to stabilize the capsid. The first ϳ60 residues at the N-terminal region interact with the RNA interior. Between this region (R) and the S domain are ϳ30 residues that act as a flexible connecting arm. The S domain is ϳ170 residues and forms a tight protein shell around the RNA genome. The final ϳ115 residues form the P domains, which combine with the adjacent subunit's P domains to form dimeric protrusions from the shell. The A subunits lie immediately adjacent to the icosahedral 5-fold axes, and their P domains interact with the P domains of adjacent B subunits to form 60 of the 90...

show abstract

supporting

confidence: 71%

supporting

confidence: 56%

See 1 more Smart Citation

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

Kakani

Katpally

et al. 2013

J Virol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Recent cryoelectron microscopy studies have shown that the CNV particle is a Tϭ3 icosahedron whose structure is highly similar to that of TBSV, the type member of the Tombusvirus genus (21). Each of the 180 CP subunits that comprise the CNV particle consists of three major domains: an N-terminal 58-amino-acid (aa) Rdomain, a shell domain (S-domain), and a protruding domain (P-domain) (Fig.…”

mentioning

confidence: 99%

“…1). The R-domain, which is highly basic, is present within the interior of the particle, where it binds RNA and in addition is likely to comprise part of the recently described highly structured inner shell of the CNV virion (21). The S-domain forms the outer shell, and the P-domain projects from the surface of the particle.…”

mentioning

confidence: 99%

Induction of Particle Polymorphism by Cucumber Necrosis Virus Coat Protein Mutants In Vivo

Kakani

Reade

Katpally

et al. 2008

J Virol

Self Cite

View full text Add to dashboard Cite

The Cucumber necrosis virus (CNV) particle is a T‫3؍‬ icosahedron consisting of 180 identical coat protein (CP) subunits. Plants infected with wild-type CNV accumulate a high number of T‫3؍‬ particles, but other particle forms have not been observed. Particle polymorphism in several T‫3؍‬ icosahedral viruses has been observed in vitro following the removal of an extended N-terminal region of the CP subunit. In the case of CNV, we have recently described the structure of T‫1؍‬ particles that accumulate in planta during infection by a CNV mutant (R1؉2) in which a large portion of the N-terminal RNA binding domain (R-domain) has been deleted. In this report we further describe properties of this mutant and other CP mutants that produce polymorphic particles. The T‫1؍‬ particles produced by R1؉2 mutants were found to encapsidate a 1.9-kb RNA species as well as smaller RNA species that are similar to previously described CNV defective interfering RNAs. Other R-domain mutants were found to encapsidate a range of specifically sized less-than-full-length CNV RNAs. Mutation of a conserved proline residue in the arm domain near its junction with the shell domain also influenced T‫1؍‬ particle formation. The proportion of polymorphic particles increased when the mutation was incorporated into R-domain deletion mutants. Our results suggest that both the R-domain and the arm play important roles in the formation of T‫3؍‬ particles. In addition, the encapsidation of specific CNV RNA species by individual mutants indicates that the R-domain plays a role in the nature of CNV RNA encapsidated in particles.

show abstract

Tombusviridae

Sit¹,

Lommel²

2010

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

The Tombusviridae is a relatively large and diverse family of soil‐borne viruses that have single‐stranded, positive‐sense, RNA ( ribonucleic acid ) genomes and that share morphological, structural, molecular and genetic features. Their high titres, compact genomes and extremely stable virions lend to their attractiveness as research subjects. Indeed, the Tombusviridae are a particularly well‐characterized family of viruses in the areas of virus structure, gene expression strategies, virus movement, the support of satellite viruses and defective‐interfering RNAs as well as RNA recombination. Although the RNA‐dependent RNA polymerases share a great deal of sequence identity, the capsid proteins can be separated by the presence (or absence) of a C ‐terminal protruding domain which gives the virions a bumpy appearance in electron micrographs. Transmission of several members by fungal zoospores in a species‐specific manner has been reported. The virions of several members have been utilized for biotechnology purposes. Key Concepts: Virions are nonenveloped and extremely stable. Tombusviridae species replicate to high titres within their host cells. RNA genomes are small with a limited number of gene products that serve multiple functions. RNA–RNA interactions control gene expression in several genera. Viral‐encoded suppressors of RNA silencing act at several different stages in the response cascade. Several members transmitted through soil by specific fungal zoospores.

show abstract

Structures of T=1 and T=3 Particles of Cucumber Necrosis Virus: Evidence of Internal Scaffolding

Cited by 24 publications

References 41 publications

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

Atomic Structure of Cucumber Necrosis Virus and the Role of the Capsid in Vector Transmission

Induction of Particle Polymorphism by Cucumber Necrosis Virus Coat Protein Mutants In Vivo

Tombusviridae

Contact Info

Product

Resources

About