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Molecular characterization of the S proteins of two enterotropic murine coronavirus strains
S Kunita1, L Zhang, F R Homberger
1Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06520-8016, USA.
Abstract:
Enterotropic strains of murine coronaviruses (MHV-Y and MHV-RI) differ extensively in their pathogenesis from the prototypic respiratory strains of murine coronaviruses. In an effort to determine which viral proteins might be determinants of enterotropism, immunoblots of MHV-Y and MHV-RI virions using anti-S, -N and -M protein-specific antisera were performed. The uncleaved MHV-Y and MHV-RI S proteins migrated slightly faster than the MHV-A59 S protein. The MHV-Y S protein was inefficiently cleaved. The MHV-Y, MHV-RI and MHV-A59 N and M proteins showed only minor differences in their migration. The S genes of MHV-Y and MHV-RI were cloned, sequenced and found to encode 1361 and 1376 amino acid long proteins, respectively. The presence of several amino acids changes upstream from the predicted cleavage site of the MHV-Y S protein may contribute its inefficient cleavage. A high degree of homology was found between the MHV-RI and MHV-4 S proteins, whereas the homology between the MHV-Y S protein and the S proteins of other MHV strains was much lower. These results indicate that the enterotropism of MHV-RI and MHV-Y may be determined by different amino acid changes in the S protein and/or by changes in other viral proteins.
Insights
Murine coronavirus (MHV) strains enterotropic for the gut show different pathogenesis. Differences in the viral spike (S) protein, including its cleavage and amino acid sequence, may determine this enterotropism, potentially involving other viral proteins as well.
Area of Science:
- Virology
- Molecular Biology
- Pathogenesis
Background:
- Enterotropic murine coronaviruses (MHV-Y, MHV-RI) exhibit distinct pathogenesis compared to respiratory strains.
- Identifying viral protein determinants of enterotropism is crucial for understanding MHV disease.
Purpose of the Study:
- To investigate the role of viral proteins, particularly the spike (S) protein, in the enterotropism of MHV-Y and MHV-RI.
- To compare the S proteins of enterotropic MHV strains with other MHV strains.
Main Methods:
- Immunoblotting of MHV virions with specific antisera against S, N, and M proteins.
- Cloning and sequencing of the S genes from MHV-Y and MHV-RI.
- Analysis of amino acid sequences and protein migration patterns.
Main Results:
- MHV-Y and MHV-RI S proteins showed slightly faster migration than MHV-A59 S protein.
- MHV-Y S protein exhibited inefficient cleavage, potentially due to upstream amino acid changes.
- High homology was observed between MHV-RI and MHV-4 S proteins; MHV-Y S protein showed lower homology to other MHV strains.
Conclusions:
- Enterotropism in MHV-RI and MHV-Y may be mediated by distinct amino acid alterations within the S protein.
- Changes in other viral proteins might also contribute to the enterotropic phenotype of these MHV strains.