Abstract
The influence of tobacco mosaic virus (TMV) infection on nucleotide binding and phosphorylation of an Mr 68,000 host-encoded protein (p68) was examined. The phosphorylation of p68 in homogenates from TMV-infected tissues was 4-fold greater than in homogenates from mock inoculated tissues. Phosphorylation of p68 in extracts from mock inoculated tissues was enhanced by the addition of double-stranded (ds) RNA. Nucleotide photoaffinity labeling experiments indicate that p68 contains an ATP binding site with characteristics consistent with protein kinase activity. Antiserum raised against a dsRNA-dependent protein kinase activity. Antiserum raised against a dsRNA-dependent protein kinase from interferon-treated human cells immunoprecipitated p68 from extracts of TMV-infected tissue, and p68-containing immunocomplexes catalyzed the phosphorylation of endogenous p68. These data suggest that p68 may be an autophosphorylating, dsRNA-dependent protein kinase involved in viral pathogenesis. Based upon analogous functions demonstrated for dsRNA-dependent protein kinases in mammalian systems, p68 may have a role in the regulation of protein synthesis and viral replication in infected cells.
Highlights
The influence of tobacco mosaicvirus (TMV) infec- served as a model for studying structure-function relationtion on nucleotide binding and phosphorylation of an ships involving nucleotide-protein interactions
During studieson nucleotide-protein interactions regulated by viral pathogenesis, we identified an M, 68,000 (p68) hostman cells immunoprecipitated p68 from extracts of encoded protein whose phosphorylation is significantly in
Mock inoculated and TMV-infected tissueswere treated identically and equal amounts of each extract were loaded onto SDS
Summary
Protein-An M , 68,000 protein (p68) was present in extracts from both the infected and mock inoculated tissues. Mock inoculated and TMV-infected tissueswere treated identically. In both treatments, p68 was stained by Coomassie Blue a t approximately thesame intensity. Gel scanning confirmed that equal concentrations of p68 were. Present in both treatments;overall, approximately 10%more protein was present ongels from virus-infected tissue extracts. Incorporation of 32Pfrom [y3'P]ATP into two bands in the region of M , 68,000 from both infected and mock inoculated
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