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The Structure of Tobacco Mosaic Virus and Its Components: Ultraviolet Optical Rotatory Dispersion
Biophysical Journal
|May 12, 2009
Summary
Optical rotatory dispersion studies reveal insights into tobacco mosaic virus (TMV) structure. The protein subunits of TMV contain significant alpha-helix content, localized in their central region.
Area of Science:
- Biophysics
- Structural Biology
- Molecular Virology
Background:
- Understanding the structural properties of viruses like tobacco mosaic virus (TMV) is crucial for virology and molecular biology.
- Optical rotatory dispersion (ORD) is a technique sensitive to the secondary structure of macromolecules, particularly helical content.
Purpose of the Study:
- To investigate the optical rotatory dispersion (ORD) of tobacco mosaic virus (TMV) and its constituent components.
- To determine the secondary structure, specifically alpha-helix content, of TMV protein subunits.
- To analyze the structural changes in TMV components under different conditions, such as in urea solutions.
Main Methods:
- Measurement of optical rotatory dispersion (ORD) in the wavelength region of 226 to 366 mmu.
- Analysis of ORD spectra for TMV, isolated protein subunits, synthesized protein rods, and isolated ribonucleic acid (RNA).
- Investigation of the effect of concentrated urea solution on the ORD of TMV RNA.
Main Results:
- Both intact TMV and synthesized protein rods exhibited anomalous rotatory dispersion.
- TMV RNA showed a Cotton effect with an inflection point at 260 mmu, shifting to 272 mmu in urea.
- TMV protein subunits displayed an incipient Cotton effect (inflection point ~293 mmu) and a negative Cotton effect (trough at 232 mmu), indicating 25-35% alpha-helix content.
Conclusions:
- The protein subunits of TMV possess a significant alpha-helix content, estimated between 25% and 35%.
- The helical regions within the protein subunits are likely located in the central part of the polypeptide chain.
- ORD is a valuable tool for elucidating the structural organization of viral components and their conformational changes.
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