Intracellular phosphorylation of the Sendai virus P protein.

Abstract

Phosphorylation status of the Sendai virus P protein was examined during virus infection and compared with cell-free phosphorylation. P protein from Sendai virus-infected (VI) and P/C gene-transfected (PT) mammalian cells and from purified virions (PV) was phosphorylated at only serine residues. In contrast, cell-free phosphorylation of the P protein with virion-associated protein kinase (VAPK) occurred at both threonine and serine. Tryptic phosphopeptide maps of the P protein from VI, PT, and PV showed that the phosphorylation was primarily localized on one peptide (TP1), while VAPK phosphorylated the P protein on several peptides. There was no change in the steady-state phosphopeptide map of the P protein during virus replication, indicating that the TP1 is constitutively phosphorylated. Inhibition of cellular phosphatases (PP1 and PP2A) by okadaic acid (OA) in virus-infected cells caused a sixfold increase in the P protein phosphorylation, solely at serine residues. The phosphopeptide map of the OA-P protein revealed that phosphorylation occurred on several peptides, but the OA-P map was significantly different from the VAPK-P map. However, additional phosphorylation of the P protein did not block its association with nucleocapsids. These results suggest that the Sendai virus P protein is constitutively phosphorylated primarily at one locus but has the potential for phosphorylation at additional sites. Further, our results do not show any correlations between the intracellular and cell-free phosphorylation of the P protein and, therefore, question the validity of cell-free phosphorylations.

• Authors: S Byrappa, D D Hendricks, Y B Pan, J M Seyer, K C Gupta
• Journal: Virology (Virology) Vol. 208 Issue 1 Pg. 408-13 (Apr 01 1995) ISSN: 0042-6822 [Print] United States
• PMID: 11831729 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• P protein, Sendai virus
• Phosphoproteins
• Viral Proteins

Topics

• Animals
• COS Cells
• Cell-Free System
• Phosphoproteins (physiology)
• Phosphorylation
• Sendai virus (physiology)
• Viral Proteins (physiology)
• Virus Replication