The mumps virus SH protein is a membrane protein and not essential for virus growth.

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.