title: Structural basis of nSH2 regulation and lipid binding in PI3Kα.
abstract: We report two crystal structures of the wild-type phosphatidylinositol 3-kinase α (PI3Kα) heterodimer refined to 2.9 Å and 3.4 Å resolution: the first as the free enzyme, the second in complex with the lipid substrate, diC4-PIP₂, respectively. The first structure shows key interactions of the N-terminal SH2 domain (nSH2) and iSH2 with the activation loop that suggest a mechanism by which the enzyme is inhibited in its basal state. In the second structure, the lipid substrate binds in a positively charged pocket adjacent to the ATP-binding site, bordered by the P-loop, the activation loop and the iSH2 domain. An additional lipid-binding site was identified at the interface of the ABD, iSH2 and kinase domains. The ability of PI3Kα to bind an additional PIP₂ molecule was confirmed in vitro by fluorescence quenching experiments. The crystal structures reveal key differences in the way the nSH2 domain interacts with wild-type p110α and with the oncogenic mutant p110αH1047R. Increased buried surface area and two unique salt-bridges observed only in the wild-type structure suggest tighter inhibition in the wild-type PI3Kα than in the oncogenic mutant. These differences may be partially responsible for the increased basal lipid kinase activity and increased membrane binding of the oncogenic mutant.
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia. Present Address: Department of Oncology, Johns Hopkins University School of Medicine, Baltimore Maryland, USA.
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Miller
authors.affiliation: Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institutions, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Present Address: Sanofi, Cambridge, Massachusetts. Present Address: Berkeley Center for Structural Biology, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California.
authors.forename: Oleg
authors.initials: O
authors.lastname: Schmidt-Kittler
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Present Address: Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: David M
authors.initials: DM
authors.lastname: Bolduc
authors.affiliation: Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institutions, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Present Address: Paragon Bioservices, Baltimore, Maryland.
authors.forename: Evan T
authors.initials: ET
authors.lastname: Brower
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Daniele
authors.initials: D
authors.lastname: Chaves-Moreira
authors.affiliation: Photon Sciences, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Allaire
authors.affiliation: Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institutions, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Kinzler
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Jennings
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Thompson
authors.affiliation: Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Cole
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: L Mario
authors.initials: LM
authors.lastname: Amzel
authors.affiliation: Ludwig Center for Cancer Genetics and Therapeutics and Howard Hughes Medical Institutions, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Bert
authors.initials: B
authors.lastname: Vogelstein
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Sandra B
authors.initials: SB
authors.lastname: Gabelli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001896:Boron Compounds / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D061987:Sf9 Cells; D015398:Signal Transduction; D018411:Spodoptera; D018909:src Homology Domains
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D019869:Phosphatidylinositol 3-Kinases
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