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Picornaviral VPg sequences are contained in the replicase precursor
Abstract:
It has previously been shown that the RNA replicase of encephalomyocarditis virus contains two virus-coded proteins, D and E, which are produced in two successive proteolytic steps: (i) C leads to D + ?; and (ii) D leads to p22 + E. It is here shown (i) that virus protein H (molecular weight, 12,000) is the previously unidentified product of the first step and (ii) that VPg, a protein linked covalently to the virion RNA, yields two tryptic peptides found in protein C but not in protein D. The results suggest that VPg is derived by cleavage of protein C and that protein H may be intermediate. Preliminary experiments with VPg sequences in polioviral noncapsid protein 1b, the counterpart of encephalomyocarditis viral protein C, were inconclusive.
Insights
Encephalomyocarditis virus RNA replicase processing reveals new viral proteins. Protein H is identified as a product of proteolytic cleavage, and VPg is suggested to derive from protein C.
Area of Science:
- Virology
- Molecular Biology
- Proteomics
Background:
- The RNA replicase of encephalomyocarditis virus (EMCV) is crucial for viral replication.
- Previous studies identified two virus-coded proteins, D and E, from proteolytic processing of the replicase.
- The precise intermediates and products of these processing steps were not fully elucidated.
Purpose of the Study:
- To identify the previously unknown product of the first proteolytic step in EMCV RNA replicase processing.
- To investigate the relationship between virion-linked protein VPg and the viral proteins C and D.
- To explore the potential role of protein H as an intermediate in viral protein processing.
Main Methods:
- Proteolytic cleavage analysis of EMCV RNA replicase components.
- Identification of viral protein products using molecular weight determination.
- Tryptic peptide mapping of VPg and viral proteins C and D.
Main Results:
- Virus protein H (12,000 molecular weight) was identified as the missing product of the initial proteolytic cleavage step.
- VPg yielded tryptic peptides present in protein C but absent in protein D.
- Preliminary analysis suggested VPg is derived from protein C, with protein H potentially acting as an intermediate.
Conclusions:
- The study elucidates the proteolytic processing pathway of the EMCV RNA replicase.
- Protein H is identified as a key intermediate in the generation of mature viral proteins.
- Evidence suggests VPg is derived from protein C, contributing to our understanding of viral genome-protein interactions.