Topography of murine leukemia virus envelope proteins: characterization of transmembrane components

Area of Science:

• Virology
• Molecular Biology
• Protein Chemistry

Background:

• Moloney murine leukemia virus (MMLV) is a retrovirus studied for its structure and replication.
• The envelope proteins, gp70 and p15(E), are crucial for viral entry and assembly.
• Understanding the topology of viral proteins is key to deciphering viral mechanisms.

Purpose of the Study:

• To investigate the structural organization and membrane topology of the MMLV envelope proteins p15(E) and Pr15(E).
• To identify cleavage sites of p15(E) and Pr15(E) upon trypsinization of intact and solubilized MMLV.

Main Methods:

• Proteolytic digestion of intact and solubilized Moloney murine leukemia virus using trypsin.
• Analysis of protein fragments by molecular weight determination and epitope mapping.

Main Results:

• Trypsinization of intact MMLV cleaved p15(E) and Pr15(E) near the middle, yielding an N-terminal fragment containing the gp70 disulfide linkage site and epitopes b and c.
• Solubilization of the viral membrane revealed a second trypsin cleavage site near the C-terminus of p15(E).
• These findings indicate that p15(E) and Pr15(E) are transmembrane proteins with specific domains exposed on the virion surface.

Conclusions:

• The p15(E) and Pr15(E) proteins of MMLV span the viral membrane.
• Differential trypsin cleavage sites suggest distinct structural roles for these proteins in intact versus solubilized virions.
• This study elucidates the transmembrane nature of MMLV envelope proteins.