Mast cell tryptase from pig lungs triggers infection by pneumotropic Sendai and influenza A viruses: Purification and characterization
2000
Chen, Ye | Shiota, Mayumi | Ohuchi, Masanobu | Towatari, Takae | Tashiro, Junko | Murakami, Meiko | Yano, Mihiro | Yang, Bing | Kido, Hiroshi
A novel trypsinâtype serine proteinase, which processes the precursors of the envelope fusion glycoproteins of pneumotropic Sendai and human influenza A viruses, was purified to homogeneity from pig lungs. On SDS/PAGE, the purified enzyme gave a protein band corresponding to about 32âkDa, and has an apparent molecular mass of 120âkDa, as determined by gel permeation chromatography. Immunohistochemical staining with antibodies against this enzyme revealed that the enzyme is located in pig lung mast cells. The Nâterminal 44âaminoâacid sequence of the enzyme exhibits about 80% identity with those of mast cell tryptases from other species. Of the inhibitors tested, diâisopropyl fluorophosphate, antipain, leupeptin, benzamidine and a few proteinaceous inhibitors, such as mucus protease inhibitor and aprotinin, inhibited this enzyme activity. Heparin stabilized the enzyme, but highâionicâstrength conditions did not, unlike for human mast cell tryptase. The purified enzyme efficiently processed the fusion glycoprotein precursor of Sendai virus and slowly processed hemagglutinin of human influenza A virus, and triggered the infectivity of Sendai virus in a doseâdependent manner, although human mast cell tryptase β and rat mast cell tryptase (rat MCPâ7) from lungs did not process these fusion glycoproteins at all. These results suggest that mast cell tryptase in pig lungs is the possible trigger of the pneumotropic virus infections.
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