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Varicella zoster virus glycoprotein gpI is selectively phosphorylated by a virus-induced protein kinase
Abstract:
Varicella zoster virus glycoprotein I (VZV gpI; Mr 98,000) was phosphorylated in virus-infected human cell monolayers, while two other major VZV glycoproteins (gpII and gpIII) were not similarly modified. Phosphorylation of VZV gpI was not blocked by inhibitors of glycosylation, nor were the phosphoryl groups enzymatically removed by endoglycosidases. Phosphoamino acid analysis revealed the presence of phosphoserine and phosphothreonine residues on the polypeptide backbone. The selective nature of the phosphorylation event was further demonstrated in vitro by a protein kinase (Mr 50,000), which was present in virus-infected cells but absent from uninfected cells or purified virions. The enzyme catalyzed the transfer of 32Pi from [gamma-32P]ATP to gpI but not to gpII and gpIII. Like VZV gpI, this virus-induced protein kinase was also a constituent of the plasma membrane of live VZV-infected cells.
Insights
Varicella zoster virus glycoprotein I (VZV gpI) is selectively phosphorylated in infected cells. A virus-induced protein kinase found in infected cells targets VZV gpI for this modification.
Area of Science:
- Virology
- Molecular Biology
- Cellular Biochemistry
Background:
- Varicella zoster virus (VZV) is a human herpesvirus responsible for chickenpox and shingles.
- VZV encodes several glycoproteins essential for viral infectivity and host cell interaction.
- Post-translational modifications of viral proteins can significantly impact viral pathogenesis.
Purpose of the Study:
- To investigate the post-translational modification of Varicella zoster virus glycoprotein I (VZV gpI).
- To identify the mechanism and selectivity of VZV gpI phosphorylation.
- To characterize the enzyme responsible for VZV gpI phosphorylation.
Main Methods:
- Analysis of VZV-infected human cell monolayers.
- In vitro kinase assays using [gamma-32P]ATP and purified VZV glycoproteins.
- Phosphoamino acid analysis and enzymatic treatment of phosphorylated VZV gpI.
Main Results:
- Varicella zoster virus glycoprotein I (VZV gpI) undergoes selective phosphorylation in infected cells, unlike VZV gpII and gpIII.
- Phosphorylation occurs on serine and threonine residues of the polypeptide backbone and is not inhibited by glycosylation inhibitors.
- A novel virus-induced protein kinase (Mr 50,000) present in infected cells specifically phosphorylates VZV gpI in vitro and is located on the plasma membrane.
Conclusions:
- VZV gpI is selectively phosphorylated via a virus-induced protein kinase.
- This phosphorylation event is a distinct post-translational modification occurring on the polypeptide backbone.
- The virus-induced protein kinase may play a role in VZV replication or pathogenesis.