Shabb J B, Granner D K
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Mol Endocrinol. 1988 Apr;2(4):324-31. doi: 10.1210/mend-2-4-324.
The cAMP-containing phosphoform of the regulatory subunit (RII) of type II cAMP-dependent protein kinase from rat liver has been reported to have intrinsic DNA topoisomerase I activity. We found that highly purified RII preparations from eight different sources, including rat liver, contained no detectable topoisomerase I activity. Topoisomerase I exhibited an overlapping peak of activity with RII when rat liver extracts were fractionated by diethylaminoethyl-cellulose chromatography. Topoisomerase I activity was separated from RII by subsequent cAMP affinity chromatography. The results indicate that the regulatory subunit of cAMP-dependent protein kinase does not contain intrinsic topoisomerase I activity.
据报道，来自大鼠肝脏的II型环磷酸腺苷（cAMP）依赖性蛋白激酶调节亚基（RII）的含cAMP磷酸化形式具有内在的DNA拓扑异构酶I活性。我们发现，从包括大鼠肝脏在内的八个不同来源高度纯化的RII制剂中未检测到拓扑异构酶I活性。当用二乙氨基乙基纤维素色谱法分离大鼠肝脏提取物时，拓扑异构酶I与RII表现出重叠的活性峰。随后通过cAMP亲和色谱法将拓扑异构酶I活性与RII分离。结果表明，cAMP依赖性蛋白激酶的调节亚基不具有内在的拓扑异构酶I活性。
