Human Phosphoinositide 3-Kinase C2β, the Role of Calcium and the C2 Domain in Enzyme Activity
| Autor: | Marketa Zvelebil, Sandra J. Watton, Ivan Gout, Alexandre Arcaro, Stefano Volinia, Robert Stein, Michael D. Waterfield, Julian Downward, Khatereh Ahmadi, Meredith J. Layton |
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| Rok vydání: | 1998 |
| Předmět: |
Molecular Sequence Data
Lipid kinase activity Spodoptera Phosphatidylinositol 3-Kinases Biochemistry Catalysis Cell Line Substrate Specificity Wortmannin chemistry.chemical_compound Pi Animals Humans Phosphatidylinositol Cloning Molecular Protein kinase A Molecular Biology DNA Primers C2 domain Phosphoinositide 3-kinase Base Sequence biology Cell Biology Recombinant Proteins Cell biology Isoenzymes Models Chemical chemistry biology.protein Calcium Subcellular Fractions |
| Zdroj: | Journal of Biological Chemistry. 273:33082-33090 |
| ISSN: | 0021-9258 |
| Popis: | The cDNA for a human Class II phosphoinositide 3-kinase (PI 3-kinase C2beta) with a C2 domain was cloned from a U937 monocyte cDNA library and the enzyme expressed in mammalian and insect cells. Like other Class II PI 3-kinases in vitro, PI 3-kinase C2beta utilizes phosphatidylinositol (PI) and PI 4-monophosphate but not PI 4, 5-biphosphate as substrates in the presence of Mg2+. Remarkably, and unlike other PI 3-kinases, the enzyme can use either Mg-ATP or Ca-ATP to generate PI 3-monophosphate. PI 3-kinase C2beta, like the Class I PI 3-kinases, but unlike PI 3-kinase C2alpha, is sensitive to low nanomolar levels of the inhibitor wortmannin. The enzyme is not regulated by the small GTP-binding protein Ras. The C2 domain of the enzyme bound anionic phospholipids such as PI and phosphatidylserine in vitro, but did not co-operatively bind Ca2+ and phospholipids. Deletion of the C2 domain increased the lipid kinase activity suggesting that it functions as a negative regulator of the catalytic domain. Although presently it is not known whether PI 3-kinase C2beta is regulated by Ca2+ in vivo, our results suggest a novel role for Ca2+ ions in phosphate transfer reactions. |
| Databáze: | OpenAIRE |
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