Related Experiment Video
Updated: Feb 19, 2026
Advancing High-Resolution Imaging of Virus Assemblies in Liquid and Ice
Published on: July 20, 2022
Atomic force microscopy investigation of wild-type Moloney murine leukemia virus particles and virus particles
1Department of Molecular Biology and Biochemistry, University of California-Irvine, Irvine, CA 92697-3900, USA.
Abstract:
Moloney murine leukemia virus (M-MuLV) lacking the gene for the envelope glycoprotein (env(-)) was produced in NIH 3T3 cells and investigated using atomic force microscopy (AFM). The particles were compared with similarly produced wild-type virions, some of which had been exposed to a monoclonal antibody against the surface component of the envelope protein (SU protein). The env(-) particles generally exhibit a distinctly different external appearance suggesting only a low density of associated proteins that have an almost fluid, mechanically unstable character. The weakly associated proteins may be host cell membrane proteins that are incorporated into the viral membrane in place of or in addition to virus envelope protein. The amount of this non-viral protein on virion surfaces appears to vary from negligible in most cases to a substantial complement in others. It seems clear that the presence of the envelope protein, in a mechanical sense, significantly strengthens and stabilizes the virion envelope. Binding of monoclonal antibody to wild-type virions indicates that some particles expose a significant amount of antigen while adjacent virions may not. This suggests that the conformation of the envelope glycoprotein or the disposition of oligosaccharides may be different among particles, on some virions exposing the specific epitope, and others little or none.
Insights
Moloney murine leukemia virus lacking envelope proteins are mechanically unstable, suggesting host proteins may compensate. Envelope proteins are crucial for virion stability and antigen exposure varies among wild-type particles.
Area of Science:
- Virology
- Biophysics
- Cell Biology
Background:
- Moloney murine leukemia virus (M-MuLV) is a retrovirus.
- The viral envelope glycoprotein (env) is essential for infectivity.
- Understanding viral particle structure and stability is key to virology.
Purpose of the Study:
- To investigate the structural and mechanical properties of M-MuLV lacking envelope proteins (env(-)).
- To compare the surface characteristics of env(-) particles with wild-type M-MuLV.
- To assess the role of envelope proteins in virion stability.
Main Methods:
- Production of env(-) M-MuLV and wild-type M-MuLV in NIH 3T3 cells.
- Atomic force microscopy (AFM) for high-resolution imaging of viral particles.
- Incubation of wild-type virions with a monoclonal antibody against the SU protein.
Main Results:
- Env(-) M-MuLV particles displayed a different external appearance, indicating low-density, mechanically unstable associated proteins.
- These associated proteins are likely host cell membrane proteins incorporated into the viral envelope.
- Wild-type virions showed variable antigen exposure upon antibody binding, suggesting conformational differences in envelope glycoproteins.
Conclusions:
- Viral envelope proteins significantly strengthen and stabilize the M-MuLV virion envelope.
- The composition and mechanical stability of the viral envelope are influenced by the presence or absence of env proteins.
- Variability in envelope glycoprotein conformation or oligosaccharide display affects antigenicity in wild-type M-MuLV.
