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In vivo proteins of defective interfering particles of poliovirus
Abstract:
DX particles of poliovirus are deletion mutants that do not induce synthesis of capsid proteins or the precursor of capsid proteins (NCVPla) during infection. However, cells infected with DX particles synthesize two proteins, p68 and p25, that are not detected during growth of standard virus, and a protein of 27 000 (p27) which is comparable in molecular weight to VP3. Peptide maps of these proteins were obtained by partial digestion with Staphylococcus aureus V8 protease and elastase. The peptide map of p68 corresponded approximately 70% with the peptide map of NCVPla, and antiserum against virions reacted with p68. These data suggest that p68 is a large fragment of NCVPla. Digestion of purified structural proteins VP1, VP2, and VP3 yielded distinct peptide maps, but p25 was resistant to both V8 protease and elastase and did not react noticeably with anticapsid antibody. Peptide maps obtained for in vivo viral proteins migrating with a molecular weight of 27 000 were complex, indicating the presence of at least two and possibly three proteins. Cells infected with standard gs and gr viruses produced authentic VP3, but cells infected with defective interfering particles did not. However, one gr variant of standard virus contained a mutation in structural protein VP2.
Insights
Poliovirus DX particles produce unique proteins, including p68, a fragment of NCVPla, and resistant p25. These findings advance understanding of poliovirus defective interfering particles and their protein synthesis.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Background:
- Poliovirus DX particles are deletion mutants that disrupt normal capsid protein synthesis.
- Infection with DX particles leads to the production of novel viral proteins not seen in standard poliovirus infections.
Purpose of the Study:
- To characterize the novel proteins synthesized during poliovirus DX particle infection.
- To determine the relationship of these novel proteins to known poliovirus proteins and structural components.
Main Methods:
- Partial digestion of synthesized proteins (p68, p25, p27) using Staphylococcus aureus V8 protease and elastase.
- Peptide mapping to compare protein fragments.
- Antiserum against poliovirus virions was used for immunological detection.
Main Results:
- Protein p68 showed significant peptide map homology (approx. 70%) with the non-capsid precursor polyprotein (NCVPla) and reacted with anti-virion antiserum, suggesting it is a large NCVPla fragment.
- Protein p25 was resistant to enzymatic digestion and did not react with anticapsid antibodies.
- Peptide maps of p27 indicated the presence of at least two to three distinct proteins, and authentic VP3 was absent in cells infected with DX particles.
Conclusions:
- Poliovirus DX particles yield unique protein products, including a significant fragment of the non-capsid precursor polyprotein (p68).
- The protein p25 represents a novel viral product with unique resistance properties.
- These findings contribute to understanding the complex protein expression strategies of poliovirus defective interfering particles.