Picornaviral VPg sequences are contained in the replicase precursor.

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.