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Recombinant tobacco mosaic virus movement protein is an RNA-binding, alpha-helical membrane protein
Abstract:
The 30-kDa movement protein (MP) is essential for cell-cell spread of tobacco mosaic virus in planta. To explore the structural properties of MP, the full-length recombinant MP gene was expressed in Escherichia coli, and one-step purification from solubilized inclusion bodies was accomplished by using anion exchange chromatography. Soluble MP was maintained at >4 mg/ml without aggregation and displayed approximately 70% alpha-helical conformation in the presence of urea and SDS. A trypsin-resistant core domain of the MP had tightly folded tertiary structure, whereas 18 aa at the C terminus of the monomer were rapidly removed by trypsin. Two hydrophobic regions within the core were highly resistant to proteolysis. Based on results of CD spectroscopy, trypsin treatment, and MS, we propose a topological model in which MP has two putative alpha-helical transmembrane domains and a protease-sensitive carboxyl terminus.
Insights
The movement protein (MP) of tobacco mosaic virus is crucial for plant cell-to-cell spread. Structural analysis reveals a protease-resistant core and a flexible C-terminus, informing its function in viral transmission.
Area of Science:
- Plant virology
- Molecular biology
- Protein structure analysis
Background:
- Tobacco mosaic virus (TMV) movement protein (MP) facilitates cell-to-cell transport of viral RNA in plants.
- Understanding MP structure is key to elucidating its role in viral pathogenesis and spread.
Purpose of the Study:
- To investigate the structural properties of the 30-kDa TMV movement protein (MP).
- To determine the protein's folding, stability, and domain organization.
Main Methods:
- Expression of full-length recombinant MP in Escherichia coli.
- Purification using anion exchange chromatography.
- Analysis of protein conformation and stability using CD spectroscopy, SDS-PAGE, and trypsin digestion.
- Mass spectrometry (MS) for domain identification.
Main Results:
- Soluble MP maintained high concentration (>4 mg/ml) without aggregation.
- MP exhibited ~70% alpha-helical structure in the presence of urea and SDS.
- A trypsin-resistant core domain with tightly folded tertiary structure was identified.
- The C-terminal 18 amino acids were rapidly degraded by trypsin, indicating protease sensitivity.
Conclusions:
- MP possesses a stable, protease-resistant core domain.
- The C-terminus is flexible and susceptible to proteolysis.
- A topological model suggests two transmembrane domains and a protease-sensitive C-terminus for MP.