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- PDB-9nlc: Cryo-EM structure of the Class 1 PI3K alpha/KRas complex on POPC/... -

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Entry
Database: PDB / ID: 9nlc
TitleCryo-EM structure of the Class 1 PI3K alpha/KRas complex on POPC/POPS nanodiscs low-pass filtered to 10 angstroms
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 / 1-phosphatidylinositol-3-kinase regulator activity / T follicular helper cell differentiation / positive regulation of endoplasmic reticulum unfolded protein response / phosphatidylinositol kinase activity / regulation of actin filament organization / negative regulation of actin filament depolymerization / phosphatidylinositol 3-kinase activator activity ...perinuclear endoplasmic reticulum membrane / regulation of toll-like receptor 4 signaling pathway / response to muscle inactivity / 1-phosphatidylinositol-3-kinase regulator activity / T follicular helper cell differentiation / positive regulation of endoplasmic reticulum unfolded protein response / phosphatidylinositol kinase activity / regulation of actin filament organization / negative regulation of actin filament depolymerization / phosphatidylinositol 3-kinase activator activity / phosphatidylinositol 3-kinase regulator activity / response to butyrate / IRS-mediated signalling / interleukin-18-mediated signaling pathway / phosphatidylinositol 3-kinase regulatory subunit binding / PI3K events in ERBB4 signaling / neurotrophin TRKA receptor binding / response to L-leucine / positive regulation of focal adhesion disassembly / cellular response to hydrostatic pressure / Activated NTRK2 signals through PI3K / cis-Golgi network / ErbB-3 class receptor binding / transmembrane receptor protein tyrosine kinase adaptor activity / negative regulation of stress fiber assembly / Activated NTRK3 signals through PI3K / phosphatidylinositol 3-kinase complex, class IB / phosphatidylinositol 3-kinase complex / TORC2 signaling / Co-stimulation by ICOS / RHOD GTPase cycle / positive regulation of protein localization to membrane / Signaling by cytosolic FGFR1 fusion mutants / vasculature development / Nephrin family interactions / positive regulation of filopodium assembly / anoikis / kinase activator activity / Signaling by LTK in cancer / RHOF GTPase cycle / 1-phosphatidylinositol-4-phosphate 3-kinase activity / Signaling by LTK / RND1 GTPase cycle / phosphatidylinositol 3-kinase complex, class IA / RND2 GTPase cycle / MET activates PI3K/AKT signaling / PI3K/AKT activation / RND3 GTPase cycle / phosphatidylinositol-4,5-bisphosphate 3-kinase / 1-phosphatidylinositol-4,5-bisphosphate 3-kinase activity / natural killer cell mediated cytotoxicity / growth hormone receptor signaling pathway / relaxation of cardiac muscle / insulin binding / phosphatidylinositol 3-kinase / phosphatidylinositol-3-phosphate biosynthetic process / Signaling by ALK / cardiac muscle cell contraction / RHOV GTPase cycle / RHOB GTPase cycle / vascular endothelial growth factor signaling pathway / GP1b-IX-V activation signalling / 1-phosphatidylinositol-3-kinase activity / Erythropoietin activates Phosphoinositide-3-kinase (PI3K) / PI-3K cascade:FGFR3 / response to dexamethasone / negative regulation of macroautophagy / response to mineralocorticoid / GMP binding / PI-3K cascade:FGFR2 / PI-3K cascade:FGFR4 / PI-3K cascade:FGFR1 / LRR domain binding / RHOC GTPase cycle / RHOJ GTPase cycle / response to isolation stress / phosphatidylinositol phosphate biosynthetic process / response to gravity / Synthesis of PIPs at the plasma membrane / positive regulation of protein kinase activity / RHOU GTPase cycle / myoblast proliferation / response to muscle stretch / phosphatidylinositol-mediated signaling / CDC42 GTPase cycle / RET signaling / cardiac muscle cell proliferation / negative regulation of anoikis / T cell differentiation / Interleukin-3, Interleukin-5 and GM-CSF signaling / PI3K events in ERBB2 signaling / RHOG GTPase cycle / Signaling by RAS GAP mutants / Signaling by RAS GTPase mutants / Activation of RAS in B cells / insulin receptor substrate binding / PI3K Cascade / Role of LAT2/NTAL/LAB on calcium mobilization / RAC3 GTPase cycle / RHOA GTPase cycle
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. / Src homology 2 domains / SH2 domain / Src homology 3 domains / Rab subfamily of small GTPases / 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: 10 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
Citation
Journal: Mol Cell / Year: 2026
Title: Structures of the PI3Kα/KRas complex on lipid bilayers reveal molecular mechanisms of PI3Kα activation.
Authors: Hayarpi Torosyan / Michael D Paul / Brigitte G Meyer / Allison Maker / 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. To understand the molecular mechanism of PI3Kα activation, we used ...PI3Kα is a potent oncogene that converts PIP2 to PIP3 at the plasma membrane upon activation by receptor tyrosine kinases and Ras. To understand the molecular mechanism of PI3Kα activation, we used cryo-electron microscopy to visualize the conformational states that underlie its transition to an active signaling complex. Here, we present structures of the PI3Kα/KRas complex embedded in lipid nanodiscs, revealing a rich ensemble of PI3Kα conformations that capture the progressive release of key inhibitory domains from the PI3Kα catalytic core. PIP2 triggers significant restructuring of active site regulatory motifs while an 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, dimeric PI3Kα amplifies Akt signaling in response to growth factor stimulation. Collectively, these structures map the conformational landscape of PI3Kα activation and reveal previously unexplored interfaces for potential therapeutic targeting.
#1: Journal: 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
DepositionMar 3, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0May 13, 2026Provider: repository / Type: Initial release
Revision 1.0May 13, 2026Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0May 13, 2026Data content type: Half map / Part number: 1 / Data content type: Half map / Provider: repository / Type: Initial release
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Revision 1.0May 13, 2026Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0May 13, 2026Data content type: Mask / Part number: 1 / Data content type: Mask / Provider: repository / Type: Initial release
Revision 1.0May 13, 2026Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release
Revision 1.1Jul 22, 2026Group: Data collection / Database references / Category: citation / citation_author / em_admin / Item: _em_admin.last_update
Revision 1.1Jul 22, 2026Data content type: EM metadata / Data content type: EM metadata / EM metadata / Group: Database references / Experimental summary / Data content type: EM metadata / EM metadata / EM metadata / Category: citation / citation_author / em_admin / Data content type: EM metadata / Item: _em_admin.last_update
Revision 1.2Jul 29, 2026Group: Data collection / Database references / Category: citation / em_admin
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Revision 1.2Jul 29, 2026Data content type: EM metadata / Data content type: EM metadata / EM metadata / Group: Database references / Experimental summary / Data content type: EM metadata / EM metadata / Category: citation / em_admin / Data content type: EM metadata / EM metadata / EM metadata
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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&software
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_555x,y,z1

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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: 10 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 111772 / Symmetry type: POINT

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