title: Crystal structure of the phosphatidylinositol 3,4-bisphosphate-binding pleckstrin homology (PH) domain of tandem PH-domain-containing protein 1 (TAPP1): molecular basis of lipid specificity.
abstract: Phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3)] and its immediate breakdown product PtdIns(3,4)P(2) function as second messengers in growth factor- and insulin-induced signalling pathways. One of the ways that these 3-phosphoinositides are known to regulate downstream signalling events is by attracting proteins that possess specific PtdIns-binding pleckstrin homology (PH) domains to the plasma membrane. Many of these proteins, such as protein kinase B, phosphoinositide-dependent kinase 1 and the dual adaptor for phosphotyrosine and 3-phosphoinositides (DAPP1) interact with both PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2) with similar affinity. Recently, a new PH-domain-containing protein, termed tandem PH-domain-containing protein (TAPP) 1, was described which is the first protein reported to bind PtdIns(3,4)P(2) specifically. Here we describe the crystal structure of the PtdIns(3,4)P(2)-binding PH domain of TAPP1 at 1.4 A (1 A=0.1 nm) resolution in complex with an ordered citrate molecule. The structure is similar to the known structure of the PH domain of DAPP1 around the D-3 and D-4 inositol-phosphate-binding sites. However, a glycine residue adjacent to the D-5 inositol-phosphate-binding site in DAPP1 is substituted for a larger alanine residue in TAPP1, which also induces a conformational change in the neighbouring residues. We show that mutation of this glycine to alanine in DAPP1 converts DAPP1 into a TAPP1-like PH domain that only interacts with PtdIns(3,4)P(2), whereas the alanine to glycine mutation in TAPP1 permits the TAPP1 PH domain to interact with PtdIns(3,4,5)P(3).
authors.affiliation: Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
authors.forename: C C
authors.initials: CC
authors.lastname: Thomas
authors.forename: S
authors.initials: S
authors.lastname: Dowler
authors.forename: M
authors.initials: M
authors.lastname: Deak
authors.forename: D R
authors.initials: DR
authors.lastname: Alessi
authors.forename: D M
authors.initials: DM
authors.lastname: van Aalten
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001798:Blood Proteins / Q000737:chemistry / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002951:Citrates / Q000378:metabolism; D003460:Crystallization; D005227:Fatty Acids / Q000737:chemistry / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; D002352:Carrier Proteins; D002951:Citrates; C486555:DAPP1 protein, human; D005227:Fatty Acids; D047908:Intracellular Signaling Peptides and Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; C435927:PLEKHA1 protein, human; D018129:Phosphatidylinositol Phosphates; C060980:phosphatidylinositol 3,4-diphosphate