A substantially pure 3-phosphoinositide dependent protein kinase that phosphorylates and activates protein kinase Bα. A recombinant polynucleotide encoding a protein kinase as defined. Uses of the protein kinase and polynucleotide, especially in screening for new drugs.
1. An isolated antibody reactive towards a substantially pure 3-phosphoinositide-dependent protein kinase (PDK1), wherein the 3-phosphoinositide-dependent protein kinase comprises SEQ ID NO:3, SEQ ID NO:4 or SEQ ID NO:5, or two or more of these sequences and wherein the 3-phosphoinositide-dependent protein kinase phosphorylates and activates protein kinase Bα.
2. An antibody according to claim 1 , wherein the 3phosphoinositide-dependent protein kinase is a substantially pure phosphatidylinositol-3,4,5-triphosphate dependent protein kinase.
3. An antibody according to claim 1 , wherein the 3-phosphoinositide-dependent protein kinase activates protein kinase Bα substantially in the presence of a D-enantiomer of sn-1-stearoyl-2-arachidonyl phosphatidylinositol 3,4,5-triphosphate but does not activate protein kinase Bα in the presence of an L-enantiomer of the phosphatidylinositol 3,4,5-triphosphate.
4. An antibody according to claim 1 , wherein the 3-phosphoinositide-dependent protein kinase is substantially activated by a D-enantiomer of sn-1,2-dipalmitoyl phosphatidylinositol 3,4,5-triphosphate or sn-1,2-dipalmitoyl phosphatidylinositol 3,4-biphosphate but is not substantially activated by the L-enantiomers of the phosphatidyl inositol phosphates.
5. An antibody according to claim 1 , wherein the 3-phosphoinositide-dependent protein kinase is not substantially activated by phosphatidylinositol 3,5-biphosphate or phosphatidylinositol 4,5-biphosphate or phosphatidylinositol 4phosphate or phosphatidylinositol 3-phosphate or inositol 1,3,4,5-tetrakisphosphate.
6. An antibody according to claim 1 , wherein the activity of the 3-phosphoinositide-dependent protein kinase is substantially unaffected by wortmannin.
7. An antibody according to claim 1 , wherein the 3-phosphoinositide-dependent protein kinase is isolated from rabbit skeletal muscle.
8. An antibody according to claim 1 , wherein the antibody is reactive towards a polypeptide which consists of SEQ ID NO:3, SEQ ID NO:4 or SEQ ID NO:5, or two or more of these sequences.