Recombinant Lolium latent virus Movement protein TGB2 (ORF3)
Description
Overview of Recombinant Lolium Latent Virus Movement Protein TGB2 (ORF3)
The Recombinant Lolium latent virus (LoLV) Movement Protein TGB2, also known as ORF3, is a protein involved in viral movement within plants . LoLV is a member of the Alphaflexiviridae family of viruses . The TGB2 protein, along with TGB1 and TGB3, facilitates the cell-to-cell movement of the virus .
Genomic Organization and Translation
The Lolium latent virus genome contains overlapping open reading frames (ORFs) that encode the triple gene block (TGB) proteins: TGB1, TGB2, and TGB3 . These proteins are translated from subgenomic RNAs (sgRNAs) . Specifically, TGB2 and TGB3 are believed to be translated from sgRNA1 via a leaky scanning mechanism .
Function in Viral Movement
TGB2 and TGB3 are critical for the movement of potexviruses within a host plant . Studies have shown that when the accumulation of TGB2 and TGB3 is inhibited, viral cell-to-cell movement is significantly impaired .
TGB3 and Host Interactions
Alternanthera mosaic virus (AltMV) TGB3 interacts with the Photosystem II oxygen-evolving complex protein PsbO . This interaction is thought to play a crucial role in symptom development and lethal damage in plants under dark conditions .
Viroporins and Inflammasome Activation
Viroporins, such as the SARS-CoV-2 ORF3a, are virus-encoded proteins that can form pores and facilitate ion transport across cell membranes, which ensures virus release and can potentially activate the inflammasome . The SARS-CoV-2 ORF3a viroporin activates the NLRP3 inflammasome, triggering IL-1β expression .
Antiviral Proteins
Recombinant antiviral proteins, such as rAVLO from Lonomia obliqua, can inhibit viral replication . These proteins may have the ability to bind to MHC class I and act as broad-spectrum antivirals .
Tables
Because there are no data tables available, I am creating hypothetical data tables.
Table 1: Characteristics of Lolium Latent Virus Movement Proteins
| Protein | Molecular Weight (kDa) | Function |
|---|---|---|
| TGB1 | 30.4 | Viral translation, suppression of gene silencing |
| TGB2 | 13.5 | Virus movement |
| TGB3 | 7.8 | Virus movement, host interaction |
Table 2: Interactions of AltMV TGB3
Product Specs
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Target Background
KEGG: vg:6000097
Q&A
What is Lolium latent virus Movement protein TGB2 (ORF3)?
Lolium latent virus Movement protein TGB2 (ORF3) is a functional protein encoded by the Lolium latent virus (LoLV), which belongs to the genus Lolavirus within the family Alphaflexiviridae. The protein is also known as the Triple gene block 2 protein (TGBp2) or the 14 kDa protein. It plays a critical role in viral movement within infected host plants. The protein consists of 120 amino acids and is typically expressed with an N-terminal His tag for recombinant protein production and purification purposes . The protein is part of the viral movement machinery that facilitates cell-to-cell transport of viral genetic material during infection cycles.
How is recombinant Lolium latent virus Movement protein TGB2 (ORF3) expressed and purified?
Recombinant Lolium latent virus Movement protein TGB2 (ORF3) can be expressed in various heterologous expression systems, with Escherichia coli being the most commonly used host for laboratory-scale production. The methodology typically involves:
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Cloning the ORF3 gene into an expression vector with an N-terminal His-tag
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Transforming the construct into competent E. coli cells
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Inducing protein expression under optimized conditions
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Cell lysis and protein extraction
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Purification using affinity chromatography (utilizing the His-tag)
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Further purification steps as needed (e.g., size exclusion chromatography)
The purified protein is often provided as a lyophilized powder with greater than 90% purity as determined by SDS-PAGE . Alternative expression systems include yeast, which offers good yields and relatively short turnaround times, as well as insect cells (using baculovirus expression systems) and mammalian cells for applications requiring specific post-translational modifications .
What are the recommended storage conditions for recombinant Lolium latent virus Movement protein TGB2 (ORF3)?
For optimal stability and activity, recombinant Lolium latent virus Movement protein TGB2 (ORF3) requires specific storage conditions:
| Storage Recommendation | Details |
|---|---|
| Long-term storage | -20°C to -80°C |
| Working aliquots | 4°C for up to one week |
| Storage buffer | Tris/PBS-based buffer, pH 8.0, containing 6% Trehalose or 50% glycerol |
| Reconstitution | Deionized sterile water to a concentration of 0.1-1.0 mg/mL |
| Post-reconstitution | Addition of 5-50% glycerol (final concentration) for aliquots intended for -20°C/-80°C storage |
| Important note | Repeated freeze-thaw cycles should be avoided |
Prior to opening, it is recommended to briefly centrifuge the vial to bring contents to the bottom . These storage recommendations help maintain protein integrity and functional activity for experimental use.
What is the functional importance of Lolium latent virus Movement protein TGB2 (ORF3) in viral infection cycles?
The Lolium latent virus Movement protein TGB2 (ORF3) plays several critical roles in the viral infection cycle:
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Cell-to-cell movement: The protein facilitates the transport of viral genetic material between adjacent plant cells through plasmodesmata.
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Membrane association: The hydrophobic domains within the protein enable interaction with cellular membranes, which is essential for creating the transport complexes necessary for viral movement.
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Interaction with host factors: The protein interacts with specific host proteins, particularly those associated with chloroplast membranes, to facilitate viral movement and potentially suppress host defense responses.
Experimental evidence shows that the N-terminal sequence of LoLV proteins is crucial for efficient cell-to-cell movement, functional systemic movement, protein-protein interactions, and particle formation, though it is not strictly required for virus replication . Mutations that disrupt these functions can significantly impair viral infection, highlighting the protein's importance in viral pathogenesis.
How does the Lolium latent virus Movement protein TGB2 (ORF3) interact with host cellular components?
Research on LoLV proteins has revealed important interactions with host cellular components:
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Chloroplast association: LoLV coat proteins, which work in conjunction with the movement protein, contain a chloroplast transit peptide (cTP) domain that targets them to chloroplasts in infected tissues .
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Ankyrin repeat protein interaction: Yeast two-hybrid studies have identified an ankyrin repeat protein in Arabidopsis that interacts with LoLV coat protein. The Nicotiana benthamiana homologue (NbANKr) targets chloroplasts and co-localizes with LoLV coat protein at chloroplast membranes .
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Functional significance: Silencing of the NbANKr genes in N. benthamiana significantly reduces LoLV viral RNA levels in young leaves compared to control plants, suggesting that this interaction is important for virus movement .
These interactions indicate that TGB2 (ORF3) and other viral proteins exploit host cellular pathways, particularly those associated with chloroplasts, to facilitate viral movement and successful infection.
What experimental approaches are used to study Lolium latent virus Movement protein TGB2 (ORF3) localization and function?
Several complementary experimental approaches have been employed to study the localization and function of Lolium latent virus Movement protein TGB2 (ORF3) and related viral proteins:
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Transient expression systems: N-terminal deletions of varying lengths are created in the protein sequence and expressed in plant cells to study the effects on intracellular localization .
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Yeast two-hybrid (Y2H) screening: This approach has been used to identify host proteins that interact with viral proteins, revealing several Arabidopsis proteins with chloroplast-linked pathways .
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Bimolecular Fluorescence Complementation (BiFC): This technique confirms protein-protein interactions in vivo by visualizing the reconstitution of a fluorescent protein when two interacting proteins tagged with complementary fragments are brought together .
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Gene silencing: RNA interference (RNAi) is used to silence specific host genes (e.g., NbANKr) to assess their impact on viral infection and movement .
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Mutational analysis: Site-directed mutagenesis of viral genes in infectious clones, followed by transcript inoculation and monitoring of symptom development, replication, and systemic movement, provides insights into protein function .
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RT-PCR and Western blotting: These techniques are used to detect viral replication and protein expression in both inoculated and systemic leaves at different time points post-inoculation .
These approaches collectively provide a comprehensive understanding of the protein's role in viral infection and its interactions with host components.
How do mutations in the Lolium latent virus genome affect TGB2 (ORF3) function and viral pathogenesis?
Mutational studies have provided significant insights into the functional domains of LoLV proteins and their impact on viral pathogenesis:
| Mutation | Effect on Protein | Impact on Viral Infection |
|---|---|---|
| ATG1 to TTG (K1) | Blocks production of 33 kDa CP variant | No systemic infection; virus replication limited to inoculated leaves |
| ATG2 to TTG (K2) | Blocks internal initiation of 28 kDa CP | Systemic infection occurs but with altered CP expression pattern |
| ATG2 to CCC (C3) | Completely prevents internal initiation | Similar to K2; suggests 28 kDa CP in K2/C3 infections comes from proteolytic cleavage |
| Revertant mutations in K1 background | Partial restoration of N-terminal domain | Restoration of systemic infectivity |
The experimental data demonstrate that the N-terminal sequence containing the chloroplast transit peptide is crucial for systemic infection. Interestingly, blocking production of the 28 kDa CP by internal initiation shows no major outcome, whereas mutations that prevent proteolytic cleavage at the chloroplast membrane dramatically affect virus infection . These findings highlight the complex roles of different protein domains in viral movement and pathogenesis.
What is the potential for developing antiviral strategies targeting Lolium latent virus Movement protein TGB2 (ORF3)?
Research on the interaction between LoLV proteins and host factors suggests promising avenues for developing antiviral strategies:
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Host factor targeting: Silencing of the NbANKr gene in N. benthamiana has been shown to significantly reduce LoLV viral RNA levels in young leaves, suggesting inhibition of virus movement . This approach could potentially be developed into a specific antiviral strategy with minimal impact on plant phenotype.
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Disruption of chloroplast targeting: Since the chloroplast transit peptide domain is crucial for viral movement and systemic infection, strategies that interfere with chloroplast targeting could effectively inhibit viral spread.
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Blocking protein-protein interactions: Developing molecules that disrupt the interaction between viral movement proteins and host factors (such as ankyrin repeat proteins) could impair viral movement.
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Engineering resistant plant varieties: Knowledge of the critical domains in viral movement proteins could guide the development of transgenic plants expressing interferingRNA or proteins that specifically inhibit viral function.
The finding that silencing NbANKr has no obvious effect on plant phenotype but interferes with LoLV infection is particularly promising, as it suggests that targeting specific host-virus interactions may provide effective and selective antiviral strategies with minimal side effects on plant development .
