A bacterial expression system was used to produce simian virus 40 large tumor antigen (T antigen) in the absence of the extensive posttranslational modifications that occur in mammalian cells. Wild-type T antigen produced in bacteria retained a specific subset of the biochemical activities displayed by its mammalian counterpart. Escherichia coli T antigen functioned as a helicase and bound to DNA fragments containing either site I or the wild-type origin of replication in a manner identical to mammalian T antigen. However, T antigen purified from E. coli did not efficiently bind to site II, an essential cis element within simian virus 40 origin of replication. It therefore could not unwind origin-containing plasmids or efficiently replicate simian virus 40 DNA in vitro. The ability of protein phosphorylation to modulate the intrinsic preference of full-length T antigen for either site I or site II is discussed.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 1989|
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