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Conformational maturation of measles virus nucleocapsid protein
A F Gombart1, A Hirano, T C Wong
1Department of Microbiology, University of Washington School of Medicine, Seattle 98195.
Abstract:
We have obtained a polyclonal antiserum, N-BE, against the denatured, amino-terminal half of the measles virus (MV) nucleocapsid (N) protein and a monoclonal antibody (MAb), N46, which recognizes a conformation-dependent epitope in the same region. Amino acid residues 23 to 239 were required and sufficient for the formation of the conformational epitope. Using these antibodies, we show that the N protein of MV is synthesized as a relatively unfolded protein which first appears in the free-protein pool. This nascent N protein undergoes a conformational change into a more folded mature form. This change does not require the participation of other viral proteins or genomic RNA. The mature N protein does not accumulate in the free-protein pool but is quickly and selectively incorporated into the viral nucleocapsids. The mature N protein is a target for interaction with the phosphoprotein (P protein) of MV. This interaction interferes with the recognition of the N protein by the N46 MAb. This suggests that the association with the P protein may mask the binding site for the N46 MAb or that it induces a conformational change in the N protein.
Insights
Measles virus nucleocapsid protein unfolds and folds into a mature form, independent of other viral components. This mature protein interacts with the P protein, potentially masking its structure.
Area of Science:
- Virology
- Molecular Biology
- Protein Biochemistry
Background:
- Measles virus (MV) nucleocapsid (N) protein is crucial for viral replication.
- Understanding the N protein's folding and assembly is key to MV pathogenesis.
Purpose of the Study:
- To characterize the conformational changes of the MV N protein during its synthesis and assembly.
- To investigate the role of the N protein's conformation in its interaction with other viral components.
Main Methods:
- Generation of polyclonal antiserum (N-BE) and monoclonal antibody (MAb N46) against the MV N protein.
- Analysis of N protein conformation using antibody recognition and protein folding studies.
- Investigation of N protein incorporation into nucleocapsids and interaction with the P protein.
Main Results:
- The MV N protein is initially synthesized as an unfolded protein, then undergoes a conformational maturation.
- This conformational change occurs independently of other viral proteins or genomic RNA.
- Mature N protein is rapidly incorporated into nucleocapsids and interacts with the phosphoprotein (P protein).
- Interaction with the P protein hinders recognition by MAb N46, suggesting conformational masking or alteration.
Conclusions:
- The measles virus N protein undergoes a spontaneous folding process post-synthesis.
- The P protein interaction with mature N protein may regulate its function or assembly through conformational changes.
- These findings provide insights into the molecular mechanisms of measles virus assembly and replication.