1UNP

Crystal structure of the pleckstrin homology domain of PKB alpha

Summary for 1UNP

• Entry DOI: 10.2210/pdb1unp/pdb
• Related: 1H10 1UNQ 1UNR
• Descriptor: RAC-ALPHA SERINE/THREONINE KINASE (2 entities in total)
• Functional Keywords: pleckstrin homology domain, transferase, phosphoinositide, pkb, akt
• Biological source: HOMO SAPIENS (HUMAN)
• Cellular location: Cytoplasm: P31749
• Total number of polymer chains: 1
• Total formula weight: 14542.46

Authors

Milburn, C.C.,Deak, M.,Kelly, S.M.,Price, N.C.,Alessi, D.R.,van Aalten, D.M.F. (deposition date: 2003-09-12, release date: 2004-09-16, Last modification date: 2024-11-06)

Primary citation

Milburn, C.C.,Deak, M.,Kelly, S.M.,Price, N.C.,Alessi, D.R.,Van Aalten, D.M.
Binding of phosphatidylinositol 3,4,5-trisphosphate to the pleckstrin homology domain of protein kinase B induces a conformational change.
Biochem. J., 375:531-538, 2003

PubMed Abstract: Protein kinase B (PKB/Akt) is a key regulator of cell growth, proliferation and metabolism. It possesses an N-terminal pleckstrin homology (PH) domain that interacts with equal affinity with the second messengers PtdIns(3,4,5)P3 and PtdIns(3,4)P2, generated through insulin and growth factor-mediated activation of phosphoinositide 3-kinase (PI3K). The binding of PKB to PtdIns(3,4,5)P3/PtdIns(3,4)P2 recruits PKB from the cytosol to the plasma membrane and is also thought to induce a conformational change that converts PKB into a substrate that can be activated by the phosphoinositide-dependent kinase 1 (PDK1). In this study we describe two high-resolution crystal structures of the PH domain of PKBalpha in a noncomplexed form and compare this to a new atomic resolution (0.98 A, where 1 A=0.1 nm) structure of the PH domain of PKBalpha complexed to Ins(1,3,4,5)P4, the head group of PtdIns(3,4,5)P3. Remarkably, in contrast to all other PH domains crystallized so far, our data suggest that binding of Ins(1,3,4,5)P4 to the PH domain of PKB, induces a large conformational change. This is characterized by marked changes in certain residues making up the phosphoinositide-binding site, formation of a short a-helix in variable loop 2, and a movement of variable loop 3 away from the lipid-binding site. Solution studies with CD also provided evidence of conformational changes taking place upon binding of Ins(1,3,4,5)P4 to the PH domain of PKB. Our data provides the first structural insight into the mechanism by which the interaction of PKB with PtdIns(3,4,5)P3/PtdIns(3,4)P2 induces conformational changes that could enable PKB to be activated by PDK1.

PubMed: 12964941
DOI: 10.1042/BJ20031229

Experimental method

X-RAY DIFFRACTION (1.65 Å)