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- PDB-9ni8: Cryo-EM structure of the Class 2 PI3K alpha/KRas complex on POPC/... -

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Basic information

Entry
Database: PDB / ID: 9ni8
TitleCryo-EM structure of the Class 2 PI3K alpha/KRas complex on POPC/POPS nanodiscs
Components
  • (Phosphatidylinositol ...) x 2
  • Isoform 2B of GTPase KRas
KeywordsTransferase/Hydrolase / lipid kinase / GTPase / ONCOPROTEIN / Transferase-Hydrolase complex
Function / homology
Function and homology information


perinuclear endoplasmic reticulum membrane / regulation of toll-like receptor 4 signaling pathway / response to muscle inactivity / phosphatidylinositol kinase activity / phosphatidylinositol 3-kinase regulator activity / 1-phosphatidylinositol-3-kinase regulator activity / positive regulation of endoplasmic reticulum unfolded protein response / regulation of actin filament organization / phosphatidylinositol 3-kinase activator activity / negative regulation of actin filament depolymerization ...perinuclear endoplasmic reticulum membrane / regulation of toll-like receptor 4 signaling pathway / response to muscle inactivity / phosphatidylinositol kinase activity / phosphatidylinositol 3-kinase regulator activity / 1-phosphatidylinositol-3-kinase regulator activity / positive regulation of endoplasmic reticulum unfolded protein response / regulation of actin filament organization / phosphatidylinositol 3-kinase activator activity / negative regulation of actin filament depolymerization / response to butyrate / T follicular helper cell differentiation / IRS-mediated signalling / response to L-leucine / interleukin-18-mediated signaling pathway / phosphatidylinositol 3-kinase regulatory subunit binding / myeloid leukocyte migration / PI3K events in ERBB4 signaling / neurotrophin TRKA receptor binding / positive regulation of focal adhesion disassembly / cellular response to hydrostatic pressure / autosome genomic imprinting / cis-Golgi network / Activated NTRK2 signals through PI3K / ErbB-3 class receptor binding / transmembrane receptor protein tyrosine kinase adaptor activity / negative regulation of stress fiber assembly / negative regulation of fibroblast apoptotic process / Activated NTRK3 signals through PI3K / phosphatidylinositol 3-kinase complex, class IB / phosphatidylinositol 3-kinase complex / TORC2 signaling / Co-stimulation by ICOS / RHOD GTPase cycle / Signaling by cytosolic FGFR1 fusion mutants / positive regulation of protein localization to membrane / vasculature development / regulation of cellular respiration / Nephrin family interactions / RHOF GTPase cycle / kinase activator activity / Signaling by LTK in cancer / 1-phosphatidylinositol-4-phosphate 3-kinase activity / Signaling by LTK / anoikis / positive regulation of leukocyte migration / RND1 GTPase cycle / RND2 GTPase cycle / positive regulation of filopodium assembly / RND3 GTPase cycle / relaxation of cardiac muscle / phosphatidylinositol 3-kinase complex, class IA / MET activates PI3K/AKT signaling / PI3K/AKT activation / phosphatidylinositol-4,5-bisphosphate 3-kinase / 1-phosphatidylinositol-4,5-bisphosphate 3-kinase activity / growth hormone receptor signaling pathway / phosphatidylinositol 3-kinase / insulin binding / phosphatidylinositol-3-phosphate biosynthetic process / Signaling by ALK / RHOV GTPase cycle / cardiac muscle cell contraction / 1-phosphatidylinositol-3-kinase activity / vascular endothelial growth factor signaling pathway / RHOB GTPase cycle / natural killer cell mediated cytotoxicity / response to mineralocorticoid / Erythropoietin activates Phosphoinositide-3-kinase (PI3K) / GP1b-IX-V activation signalling / GMP binding / PI-3K cascade:FGFR3 / response to dexamethasone / forebrain astrocyte development / LRR domain binding / PI-3K cascade:FGFR2 / negative regulation of macroautophagy / PI-3K cascade:FGFR4 / regulation of synaptic transmission, GABAergic / PI-3K cascade:FGFR1 / negative regulation of epithelial cell differentiation / response to isolation stress / RHOJ GTPase cycle / RHOC GTPase cycle / negative regulation of osteoclast differentiation / phosphatidylinositol phosphate biosynthetic process / response to gravity / epithelial tube branching involved in lung morphogenesis / phosphatidylinositol-mediated signaling / type I pneumocyte differentiation / Synthesis of PIPs at the plasma membrane / RHOU GTPase cycle / Rac protein signal transduction / CDC42 GTPase cycle / RET signaling / negative regulation of anoikis / myoblast proliferation / Signaling by RAS GAP mutants / Signaling by RAS GTPase mutants / Activation of RAS in B cells
Similarity search - Function
Phosphatidylinositol 3-kinase regulatory subunit alpha, SH3 domain / PIK3R1, inter-SH2 domain / PI3Kalpha, catalytic domain / PI3K p85 subunit, C-terminal SH2 domain / PI3K regulatory subunit p85-related , inter-SH2 domain / PI3K p85 subunit, N-terminal SH2 domain / Phosphatidylinositol 3-kinase regulatory subunit P85 inter-SH2 domain / PI3-kinase family, p85-binding domain / PI3-kinase family, p85-binding domain / Rho GTPase-activating protein domain ...Phosphatidylinositol 3-kinase regulatory subunit alpha, SH3 domain / PIK3R1, inter-SH2 domain / PI3Kalpha, catalytic domain / PI3K p85 subunit, C-terminal SH2 domain / PI3K regulatory subunit p85-related , inter-SH2 domain / PI3K p85 subunit, N-terminal SH2 domain / Phosphatidylinositol 3-kinase regulatory subunit P85 inter-SH2 domain / PI3-kinase family, p85-binding domain / PI3-kinase family, p85-binding domain / Rho GTPase-activating protein domain / RhoGAP domain / Rho GTPase-activating proteins domain profile. / GTPase-activator protein for Rho-like GTPases / Phosphatidylinositol 3-kinase, adaptor-binding domain / Phosphatidylinositol 3-kinase adaptor-binding (PI3K ABD) domain profile. / PI3-kinase family, Ras-binding domain / Phosphatidylinositol 3-kinase Ras-binding (PI3K RBD) domain / PI3-kinase family, ras-binding domain / Phosphatidylinositol 3-kinase Ras-binding (PI3K RBD) domain profile. / Rho GTPase activation protein / C2 phosphatidylinositol 3-kinase-type domain / Phosphoinositide 3-kinase C2 / C2 phosphatidylinositol 3-kinase (PI3K)-type domain profile. / Phosphoinositide 3-kinase, region postulated to contain C2 domain / Phosphoinositide 3-kinase family, accessory domain (PIK domain) / Phosphoinositide 3-kinase family, accessory domain (PIK domain) / Phosphoinositide 3-kinase, accessory (PIK) domain superfamily / Phosphoinositide 3-kinase, accessory (PIK) domain / Phosphatidylinositol kinase / PIK helical domain profile. / Phosphatidylinositol 3- and 4-kinases signature 1. / Phosphatidylinositol 3/4-kinase, conserved site / Phosphatidylinositol 3- and 4-kinases signature 2. / Phosphatidylinositol 3-/4-kinase, catalytic domain superfamily / Small GTPase, Ras-type / Phosphoinositide 3-kinase, catalytic domain / Phosphatidylinositol 3- and 4-kinase / Phosphatidylinositol 3- and 4-kinases catalytic domain profile. / Phosphatidylinositol 3-/4-kinase, catalytic domain / Small GTPase Ras domain profile. / Ran (Ras-related nuclear proteins) /TC4 subfamily of small GTPases / C2 domain superfamily / SH2 domain / Rho (Ras homology) subfamily of Ras-like small GTPases / Ras subfamily of RAS small GTPases / Small GTPase / Ras family / Src homology 2 (SH2) domain profile. / Rab subfamily of small GTPases / Src homology 2 domains / SH2 domain / Src homology 3 domains / SH2 domain superfamily / SH3-like domain superfamily / Src homology 3 (SH3) domain profile. / SH3 domain / Small GTP-binding protein domain / Armadillo-type fold / Ubiquitin-like domain superfamily / Protein kinase-like domain superfamily / P-loop containing nucleoside triphosphate hydrolase
Similarity search - Domain/homology
: / PHOSPHOAMINOPHOSPHONIC ACID-GUANYLATE ESTER / GTPase KRas / Phosphatidylinositol 3-kinase regulatory subunit alpha / Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform
Similarity search - Component
Biological speciesHomo sapiens (human)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.23 Å
AuthorsTorosyan, H. / Natalia, J. / Verba, K.A.
Funding support United States, 1items
OrganizationGrant numberCountry
National Institutes of Health/National Cancer Institute (NIH/NCI)U54CA274502 United States
CitationJournal: bioRxiv / Year: 2025
Title: Structures of the PI3Kα/KRas complex on lipid bilayers reveal the molecular mechanism of PI3Kα activation.
Authors: Hayarpi Torosyan / Michael D Paul / Allison Maker / Brigitte G Meyer / Natalia Jura / Kliment A Verba
Abstract: PI3Kα is a potent oncogene that converts PIP2 to PIP3 at the plasma membrane upon activation by receptor tyrosine kinases and Ras GTPases. In the absence of any structures of activated PI3Kα, the ...PI3Kα is a potent oncogene that converts PIP2 to PIP3 at the plasma membrane upon activation by receptor tyrosine kinases and Ras GTPases. In the absence of any structures of activated PI3Kα, the molecular details of its activation remain unknown. Here, we present cryo-EM structures of the PI3Kα/KRas complex embedded in lipid nanodiscs, revealing a rich ensemble of PI3Kα states adopted at the membrane surface. The sequential addition of a lipid bilayer, PIP2 and an activating phosphopeptide leads to the progressive release of key inhibitory domains from the PI3Kα catalytic core, which directly correlates with the reorganization of its active site. While association with POPC/POPS nanodiscs partially relieves PI3Kα autoinhibition, incorporation of PIP2 triggers near-complete displacement of PI3Kα inhibitory domains and significant restructuring of active site regulatory motifs. The addition of the activating phosphopeptide induces dimerization of the PI3Kα/KRas complex through a p110α catalytic subunit-mediated interface that is sterically occluded in autoinhibited PI3Kα. In cells, this dimeric PI3Kα complex amplifies Akt signaling in response to growth factor stimulation. Collectively, our structures map the conformational landscape of PI3Kα activation and reveal previously unexplored interfaces for potential therapeutic targeting.
History
DepositionFeb 25, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0May 27, 2026Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: FSC / Data content type: FSC / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: Half map / Part number: 1 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: Half map / Part number: 2 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: Mask / Part number: 1 / Data content type: Mask / Provider: repository / Type: Initial release
Revision 1.0May 27, 2026Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
A: Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform
B: Phosphatidylinositol 3-kinase regulatory subunit alpha
C: Isoform 2B of GTPase KRas
hetero molecules


Theoretical massNumber of molelcules
Total (without water)234,1786
Polymers233,0503
Non-polymers1,1283
Water00
1


  • Idetical with deposited unit
  • defined by author
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_5551

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Components

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Phosphatidylinositol ... , 2 types, 2 molecules AB

#1: Protein Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform / PtdIns-3-kinase subunit alpha / Phosphatidylinositol 4 / 5-bisphosphate 3-kinase 110 kDa catalytic ...PtdIns-3-kinase subunit alpha / Phosphatidylinositol 4 / 5-bisphosphate 3-kinase 110 kDa catalytic subunit alpha / p110alpha / Phosphoinositide-3-kinase catalytic alpha polypeptide / Serine/threonine protein kinase PIK3CA


Mass: 127822.578 Da / Num. of mol.: 1
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: PIK3CA / Production host: Spodoptera frugiperda (fall armyworm)
References: UniProt: P42336, phosphatidylinositol-4,5-bisphosphate 3-kinase, non-specific serine/threonine protein kinase
#2: Protein Phosphatidylinositol 3-kinase regulatory subunit alpha


Mass: 83710.281 Da / Num. of mol.: 1
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: PIK3R1 / Production host: Spodoptera frugiperda (fall armyworm) / References: UniProt: P27986

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Protein , 1 types, 1 molecules C

#3: Protein Isoform 2B of GTPase KRas / K-Ras 2 / Ki-Ras / c-K-ras / c-Ki-ras


Mass: 21516.656 Da / Num. of mol.: 1
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: KRAS, KRAS2, RASK2 / Production host: Trichoplusia ni (cabbage looper) / References: UniProt: P01116, small monomeric GTPase

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Non-polymers , 3 types, 3 molecules

#4: Chemical ChemComp-A1AZD / tert-butyl [2-(2-{[(2P)-2-{4-[4-(2-amino-2-oxoethyl)-2-fluoroanilino]thieno[2,3-d]pyridazin-7-yl}phenyl]oxy}ethoxy)ethyl]carbamate


Mass: 581.658 Da / Num. of mol.: 1 / Source method: obtained synthetically / Formula: C29H32FN5O5S / Feature type: SUBJECT OF INVESTIGATION
#5: Chemical ChemComp-MG / MAGNESIUM ION


Mass: 24.305 Da / Num. of mol.: 1 / Source method: obtained synthetically / Formula: Mg / Feature type: SUBJECT OF INVESTIGATION
#6: Chemical ChemComp-GNP / PHOSPHOAMINOPHOSPHONIC ACID-GUANYLATE ESTER


Mass: 522.196 Da / Num. of mol.: 1 / Source method: obtained synthetically / Formula: C10H17N6O13P3 / Feature type: SUBJECT OF INVESTIGATION
Comment: GppNHp, GMPPNP, energy-carrying molecule analogue*YM

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Details

Has ligand of interestY
Has protein modificationN

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: full-length p85 alpha and p110 alpha heterodimer/KRas complex bound to POPC/POPS/MSP1E3D1 nanodiscs
Type: COMPLEX / Entity ID: #1-#3 / Source: RECOMBINANT
Molecular weightValue: 0.232609 MDa / Experimental value: NO
Source (natural)Organism: Homo sapiens (human)
Source (recombinant)Organism: Spodoptera frugiperda (fall armyworm)
Buffer solutionpH: 7.5 / Details: 50 mM Tris-HCL, 150 mM NaCl, 1mM TCEP
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
Specimen supportGrid material: GOLD / Grid mesh size: 300 divisions/in. / Grid type: Quantifoil R1.2/1.3
VitrificationInstrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 100 % / Chamber temperature: 5 K

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: TFS KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal magnification: 105000 X / Nominal defocus max: 2000 nm / Nominal defocus min: 1000 nm / Cs: 2.7 mm
Specimen holderSpecimen holder model: FEI TITAN KRIOS AUTOGRID HOLDER
Image recordingElectron dose: 47.7 e/Å2 / Film or detector model: GATAN K3 (6k x 4k)

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Processing

EM software
IDNameVersionCategory
1cryoSPARC4.3.1particle selection
4cryoSPARC4.3.1CTF correction
7UCSF ChimeraX1.7.1model fitting
8Rosetta3model fitting
10Coot8model refinement
11ISOLDEmodel refinement
12cryoSPARC4.3.1initial Euler assignment
13cryoSPARC4.3.1final Euler assignment
15cryoSPARC4.3.13D reconstruction
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Particle selectionNum. of particles selected: 2870914
3D reconstructionResolution: 3.23 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 114960 / Symmetry type: POINT

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