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Activation of the Sendai virus fusion protein by receptor binding
F Dallocchio1, M Tomasi, T Bellini
1Dipartimento di Biochimica e Biologia Molecolare Università di Ferrara, Italy.
Abstract:
2,3 Dehydro-2-deoxy-N-acetyl-neuraminic acid (DNANA) competitively inhibits the neuraminidase activity of Hemagglutinin-neuraminidase (HN) from Sendai virus. The inhibition constant depends on the presence of the Fusion (F) protein, which is 30 microM in the presence of active F protein and 50 microM when the F protein is inactivated. These data correlate with previously reported evidence of interaction of the F protein with HN (Dallocchio, F., Tomasi, M., & Bellini, T. (1994) Biochem. Biophys. Res. Comm. 201, 988-993). Desialyzation of erythrocytes, by Clostridium neuraminidase, lowers the hemolytic activity of SV to < 0.1% of that observed on untreated erythrocytes. However, addition of DNANA causes a concentration-dependent increase of hemolytic activity. Both HN and the F protein are required for the activation of hemolytic activity by DNANA. The affinity constant for DNANA, calculated from the activation of hemolytic activity on desialyzed erythrocytes, is 35 microM, very close to the Ki for neuraminidase activity. These data suggest that the binding of the F protein to HN, induced by the binding to HN of a substrate or a substrate analogue, causes a conformational change which activates the F protein.
Insights
2,3 Dehydro-2-deoxy-N-acetyl-neuraminic acid (DNANA) inhibits Sendai virus neuraminidase activity. Its effect depends on the Fusion (F) protein, suggesting F protein activation by substrate binding to Hemagglutinin-neuraminidase (HN).
Area of Science:
- Virology
- Biochemistry
- Molecular Biology
Background:
- Sendai virus utilizes Hemagglutinin-neuraminidase (HN) for viral entry and replication.
- The Fusion (F) protein is crucial for viral membrane fusion.
- HN and F protein interactions are key to Sendai virus pathogenesis.
Purpose of the Study:
- To investigate the inhibitory effect of DNANA on HN neuraminidase activity.
- To elucidate the role of the F protein in HN activity and viral hemolysin function.
- To understand the mechanism of F protein activation by HN.
Main Methods:
- Enzyme inhibition assays using DNANA and HN.
- Hemolytic activity assays on erythrocytes.
- Investigating the influence of F protein presence and activity on HN inhibition and hemolytic activation.
Main Results:
- DNANA competitively inhibits HN neuraminidase with a Ki dependent on F protein activity (30-50 μM).
- Desialyzation of erythrocytes abolishes Sendai virus hemolytic activity, but DNANA restores it dose-dependently.
- Both HN and F proteins are essential for DNANA-induced hemolytic activity, with an affinity constant of 35 μM for DNANA.
Conclusions:
- DNANA binding to HN, potentially with F protein interaction, induces a conformational change.
- This conformational change activates the F protein, leading to increased hemolytic activity.
- The findings suggest a novel mechanism for viral protein activation mediated by substrate interaction.