passages.id: split_4_test_298_passage
passages.type: progene_text
passages.text: Its activation is initiated by the binding of 3' phosphorylated phosphoinositide lipids to its pleckstrin homology ( PH ) domain , resulting in the induction of activating phosphorylation at residues Thr308 and Ser473 by upstream kinases such as phosphoinositide - dependent protein kinase-1 ( PDK1 ) [2] .