Adenovirus type 2 coded single-stranded DNA binding protein: in vivo phosphorylation and modification

Publisher Website
Google Scholar
Abstract
The adenovirus type 2-coded single-stranded DNA binding protein (DBP) was a phosphoprotein and existed in at least 2 forms that differed in mobility by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After a 30-min pulse with [35S]methionine or 32PO4, 35S- or 32P-labeled DBP had a nominal MW of 74,000, but after a 30-min label followed by a 20-h chase, 35S- and 32P-labeled DBP had a nominal MW of 77,000. Both large and small forms of 35S- and 32P-labeled DBP bound to single-stranded DNA-cellulose columns and were eluted by 0.4 to 0.6 M NaCl; both forms also were immunoprecipitated by [goat] antiserum against adenovirus type 1-SV-40-induced [hamster] tumor cells (this antiserum contains antibodies against DBP) and by monospecific [guinea pig] antiserum against 95-99% purified DBP. With highly purified 32P-DBP labeled 7-10 h postinfection, the 32P radioactivity was firmly associated with protein material (i.e., not contaminating nucleic acids or phospholipids) and had properties expected of a phosphoester of an amino acid; paper electrophoresis of acid hydrolysates of this preparation identified phosphoserine but not phosphothreonine. Phosphoserine but not phosphothreonine was also identified in acid hydrolysates of another preparation of 32P-DBP labeled for 30 min, chased for 20 h and then immunoprecipitated by adenovirus type 1-SV-40 antiserum.