PerspectiveSignal Transduction

Update: PtdIns(3,4,5)P3 Gets Its Message Across

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Science  25 Jul 1997:
Vol. 277, Issue 5325, pp. 534
DOI: 10.1126/science.277.5325.534

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The proto-oncogene protein kinase B (PKB) is activated by the lipid second messenger phosphotidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P], but the mechanism is just now becoming clear. In this issue, Stokoe et al. show that another kinase, the upstream kinase, phosphorylates and partially activates PKB only when PtdIns(3,4,5)Pboth activates the upstream kinase and binds to PKB, causing a conformational change that seems to expose the phosphorylation site. In his Perspective, Hemmings discusses the significance of this dual regulation of this key kinase.