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The mumps virus SH protein is a membrane protein and not essential for virus growth
K Takeuchi1, K Tanabayashi, M Hishiyama
1Department of Viral Disease and Vaccine Control, National Institute of Health, Tokyo, Japan. ktake@nih.go.jp
Abstract:
By immunoprecipitation analysis using antisera against oligo peptides synthesized based on the deduced N-terminal and C-terminal amino acid sequences of the SH proteins of the mumps virus, the SH protein was detected in mumps virus-infected cells. The SH protein expressed from cDNA by the vaccinia-T7 expression system was recovered in the membrane fraction. Association of the SH protein with the membrane was resistant to high salt, EDTA, and alkaline treatment but sensitive to detergents. Indirect immunofluorescence experiments showed that the SH protein is involved in the exocytotic pathway. These data indicate that the SH protein is a membrane protein. Treatment of microsomes with TPCK-trypsin suggested that the SH protein is oriented in the membrane with its C-terminal facing the cytoplasm. Furthermore the SH protein was not detected in a particular strain (Enders strain) of mumps virus, indicating that the mumps virus SH protein is not essential for virus replication.
Insights
The mumps virus SH protein is a membrane protein involved in exocytosis, but not essential for viral replication. This finding aids in understanding mumps virus pathogenesis and potential therapeutic targets.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- The mumps virus SH protein's function and localization were previously unclear.
- Understanding viral protein interactions is crucial for developing antiviral strategies.
Purpose of the Study:
- To characterize the mumps virus SH protein's cellular localization and membrane association.
- To investigate the role of the SH protein in the viral life cycle.
Main Methods:
- Immunoprecipitation using specific antisera against SH protein peptides.
- Expression of SH protein using the vaccinia-T7 system.
- Membrane association studies with salt, EDTA, and detergents.
- Indirect immunofluorescence for cellular localization.
- TPCK-trypsin treatment of microsomes.
Main Results:
- The SH protein was detected in mumps virus-infected cells and localized to the membrane fraction.
- Membrane association was detergent-sensitive but resistant to salt, EDTA, and alkaline conditions.
- SH protein is involved in the exocytotic pathway.
- TPCK-trypsin treatment suggested C-terminal orientation towards the cytoplasm.
- SH protein was absent in the Enders strain, indicating it's non-essential for replication.
Conclusions:
- The mumps virus SH protein is a membrane-associated protein involved in the exocytotic pathway.
- Its C-terminus likely faces the cytoplasm.
- The SH protein is not essential for mumps virus replication, suggesting alternative pathways or strain-specific roles.