Recombinant Vaccinia virus Protein A34 (A34R)
Product Specs
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Target Background
Essential for the envelopment of intracellular viral particles and the egress of enveloped virions from infected cells.
Q&A
Basic Research Questions
What is the functional role of A34 in vaccinia virus morphogenesis?
A34 is a type II transmembrane glycoprotein critical for extracellular virion (EV) maturation and infectivity. Key functions include:
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Regulating EV release: A34-deficient mutants (e.g., vΔA34R) produce 19–24× more extracellular enveloped virions (EEV) but with 5–6× reduced specific infectivity due to unstable envelopes .
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Actin tail induction: A34 enables intracellular transport by promoting actin polymerization, a process abolished in A34R deletion mutants .
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Protein targeting: A34 mediates efficient incorporation of B5, A33, and A36 glycoproteins into EV membranes. In its absence, B5 accumulates in the endoplasmic reticulum (ER) .
Methodological insight: Use coimmunoprecipitation (e.g., anti-HA tagged A34) and immunofluorescence to validate interactions with B5/A36 .
How does A34’s structure influence its function?
A34 contains two domains essential for activity:
Methodological insight: Generate truncation mutants (e.g., vA34R1–70-V5) and compare phenotypes using plaque assays .
Advanced Research Questions
How do contradictory observations about A34’s role in EV release arise?
While A34 deletion increases EEV yield, these virions exhibit reduced infectivity. Contradictions stem from:
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Envelope stability: A34 stabilizes the EV membrane. Its absence causes premature envelope rupture, releasing non-infectious IMV .
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Experimental models: Cell type differences (e.g., B-SC-1 vs. HeLa) alter wrapping efficiency, skewing EEV quantification .
Methodological resolution: Quantify infectious EEV via freeze-thaw resistance assays and normalize data to total virion counts .
What strategies identify A34’s interaction partners in the EV envelope?
A34 forms a complex with B5 and A33, validated by:
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Coimmunoprecipitation: Anti-HA antibodies pull down B5 and A36 from lysates of vA34RHA-infected cells .
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Colocalization assays: Dual immunofluorescence shows A34/B5/A33 overlap at trans-Golgi network (TGN) wrapping sites .
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Genetic complementation: Coexpression of A34 with B5-GFP rescues B5’s ER retention in ΔA34R mutants .
Methodological insight: Use recombinant viruses (e.g., vB5R-GFP/ΔA34R) and subcellular fractionation to track protein trafficking .
How can A34 mutations resolve conflicting data on EV dissemination?
Point mutations in A34’s lectin-like domain (e.g., IHDJ strain) enhance EEV release without compromising infectivity . Key approaches include:
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Site-directed mutagenesis: Introduce residues (e.g., D81N) to alter glycan binding .
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Phenotypic screening: Compare plaque size, actin tail formation, and EEV stability across mutants .
Example data:
| Mutant | EEV Yield (vs. WT) | Specific Infectivity | Actin Tail Formation |
|---|---|---|---|
| ΔA34R | 24× ↑ | 16% of WT | Absent |
| A34-HA | 1.5× ↑ | 85% of WT | Reduced |
| A34 (IHDJ) | 50× ↑ | 95% of WT | Present |
Experimental Design Considerations
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Controls: Include parental WR virus and revertants (e.g., WR-rev) to distinguish A34-specific effects .
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Quantification: Use dual-fluorescent reporters (e.g., rsGFP/RFP) to track infection and transfection efficiency .
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Limitations: A34’s redundancy with F13 in IMV wrapping may confound phenotyping; use double knockouts cautiously .
