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- PDB-9nb6: Cryo-EM structure of the CD163/Hp(1-1)Hb complex -

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Basic information

Entry
Database: PDB / ID: 9nb6
TitleCryo-EM structure of the CD163/Hp(1-1)Hb complex
Components
  • (Hemoglobin subunit ...) x 2
  • Isoform 2 of Haptoglobin
  • Scavenger receptor cysteine-rich type 1 protein M130
KeywordsENDOCYTOSIS / CD163 / M130 / Scavenger receptor / Haptoglobin / Hemoglobin / Hb / Hp / HpHb / Hp(1-1)Hb / hemolysis
Function / homology
Function and homology information


negative regulation of hydrogen peroxide catabolic process / zymogen activation / CD163 mediating an anti-inflammatory response / scavenger receptor activity / nitric oxide transport / hemoglobin alpha binding / cellular oxidant detoxification / hemoglobin binding / haptoglobin-hemoglobin complex / renal absorption ...negative regulation of hydrogen peroxide catabolic process / zymogen activation / CD163 mediating an anti-inflammatory response / scavenger receptor activity / nitric oxide transport / hemoglobin alpha binding / cellular oxidant detoxification / hemoglobin binding / haptoglobin-hemoglobin complex / renal absorption / antioxidant activity / hemoglobin complex / oxygen transport / immune system process / Scavenging of heme from plasma / endocytic vesicle lumen / blood vessel diameter maintenance / acute-phase response / hydrogen peroxide catabolic process / oxygen carrier activity / carbon dioxide transport / response to hydrogen peroxide / Heme signaling / Erythrocytes take up oxygen and release carbon dioxide / Erythrocytes take up carbon dioxide and release oxygen / Late endosomal microautophagy / defense response / Cytoprotection by HMOX1 / oxygen binding / regulation of blood pressure / platelet aggregation / specific granule lumen / Chaperone Mediated Autophagy / positive regulation of nitric oxide biosynthetic process / endocytic vesicle membrane / tertiary granule lumen / Factors involved in megakaryocyte development and platelet production / scaffold protein binding / blood microparticle / ficolin-1-rich granule lumen / defense response to bacterium / iron ion binding / inflammatory response / external side of plasma membrane / serine-type endopeptidase activity / heme binding / Neutrophil degranulation / extracellular space / extracellular exosome / extracellular region / metal ion binding / membrane / plasma membrane / cytosol
Similarity search - Function
SRCR domain signature. / Scavenger receptor cysteine-rich domain / SRCR domain profile. / SRCR-like domain superfamily / Scavenger receptor Cys-rich / SRCR domain / Sushi/SCR/CCP domain / Sushi/CCP/SCR domain profile. / Sushi/SCR/CCP superfamily / Hemoglobin, pi ...SRCR domain signature. / Scavenger receptor cysteine-rich domain / SRCR domain profile. / SRCR-like domain superfamily / Scavenger receptor Cys-rich / SRCR domain / Sushi/SCR/CCP domain / Sushi/CCP/SCR domain profile. / Sushi/SCR/CCP superfamily / Hemoglobin, pi / Hemoglobin, alpha-type / Hemoglobin, beta-type / : / Globin/Protoglobin / Globin / Globin / Globin domain profile. / Globin-like superfamily / Peptidase S1A, chymotrypsin family / Serine proteases, trypsin domain profile. / Trypsin-like serine protease / Serine proteases, trypsin domain / Trypsin / Peptidase S1, PA clan, chymotrypsin-like fold / Peptidase S1, PA clan
Similarity search - Domain/homology
PROTOPORPHYRIN IX CONTAINING FE / OXYGEN MOLECULE / Haptoglobin / Hemoglobin subunit beta / Hemoglobin subunit alpha / Scavenger receptor cysteine-rich type 1 protein M130
Similarity search - Component
Biological speciesHomo sapiens (human)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.3 Å
AuthorsHuang, C.-S. / White, J.B.R. / Degtjarik, O. / Mosyak, L.
Funding support United Kingdom, 2items
OrganizationGrant numberCountry
Wellcome Trust108466/Z/15/Z United Kingdom
Wellcome Trust221524/Z/20/Z United Kingdom
CitationJournal: PLoS Biol / Year: 2025
Title: Structural elucidation of the haptoglobin-hemoglobin clearance mechanism by macrophage scavenger receptor CD163.
Authors: Ching-Shin Huang / Hui Wang / Joshua B R White / Oksana Degtjarik / Cindy Huynh / Kristoffer Brannstrom / Mark T Horn / Stephen P Muench / William S Somers / Javier Chaparro-Riggers / Laura ...Authors: Ching-Shin Huang / Hui Wang / Joshua B R White / Oksana Degtjarik / Cindy Huynh / Kristoffer Brannstrom / Mark T Horn / Stephen P Muench / William S Somers / Javier Chaparro-Riggers / Laura Lin / Lidia Mosyak /
Abstract: Intravascular hemolysis releases hemoglobin into the bloodstream, which can damage vascular and renal tissues due to its oxidative nature. Circulating haptoglobin acts as a primary defense by binding ...Intravascular hemolysis releases hemoglobin into the bloodstream, which can damage vascular and renal tissues due to its oxidative nature. Circulating haptoglobin acts as a primary defense by binding to free hemoglobin, forming a haptoglobin-hemoglobin (HpHb) complex that is then recognized and cleared by the CD163 scavenger receptor on macrophages. While the function and structure of HpHb complex are mostly well-defined, the molecular mechanism underlying its interaction with CD163 remains unclear. Here we report the cryo-electron microscopy structures of human CD163 in its unliganded state and in its complex with HpHb. These structures reveal that CD163 functions as a trimer, forming a composite binding site at its center for one protomer of the dimeric HpHb, resulting in a 3:1 binding stoichiometry. In the unliganded state, CD163 can also form a trimer, but in an autoinhibitory configuration that occludes the ligand binding site. Widespread electrostatic interactions mediated by calcium ions are pivotal in both pre-ligand and ligand-bound receptor assemblies. This calcium-dependent mechanism enables CD163/HpHb complexes to assemble and, once internalized, disassemble into individual components upon reaching the endosome, where low calcium and lower pH conditions prevail. Collectively, this study elucidates the molecular mechanism by which CD163-mediated endocytosis efficiently clears different isoforms of HpHb.
History
DepositionFeb 13, 2025Deposition site: RCSB / Processing site: RCSB
Revision 1.0Jun 18, 2025Provider: repository / Type: Initial release
Revision 1.0Jun 18, 2025Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0Jun 18, 2025Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0Jun 18, 2025Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release
Revision 1.1Jul 23, 2025Group: Data collection / Database references / Category: citation / citation_author / em_admin
Item: _citation.country / _citation.journal_abbrev ..._citation.country / _citation.journal_abbrev / _citation.journal_id_CSD / _citation.journal_id_ISSN / _citation.journal_volume / _citation.page_first / _citation.page_last / _citation.pdbx_database_id_DOI / _citation.pdbx_database_id_PubMed / _citation.title / _citation.year / _citation_author.identifier_ORCID / _citation_author.name / _em_admin.last_update

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
A: Scavenger receptor cysteine-rich type 1 protein M130
B: Scavenger receptor cysteine-rich type 1 protein M130
C: Scavenger receptor cysteine-rich type 1 protein M130
D: Hemoglobin subunit alpha
E: Hemoglobin subunit beta
F: Isoform 2 of Haptoglobin
G: Isoform 2 of Haptoglobin
hetero molecules


Theoretical massNumber of molelcules
Total (without water)441,70343
Polymers437,4937
Non-polymers4,21036
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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Protein , 2 types, 5 molecules ABCFG

#1: Protein Scavenger receptor cysteine-rich type 1 protein M130 / Hemoglobin scavenger receptor


Mass: 109731.555 Da / Num. of mol.: 3
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Homo sapiens (human) / Gene: CD163, M130 / Production host: Homo sapiens (human) / References: UniProt: Q86VB7
#4: Protein Isoform 2 of Haptoglobin / Zonulin


Mass: 38497.652 Da / Num. of mol.: 2 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P00738

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Hemoglobin subunit ... , 2 types, 2 molecules DE

#2: Protein Hemoglobin subunit alpha / Alpha-globin / Hemoglobin alpha chain


Mass: 15281.550 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P69905
#3: Protein Hemoglobin subunit beta / Beta-globin / Hemoglobin beta chain


Mass: 16021.396 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) Homo sapiens (human) / References: UniProt: P68871

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Sugars , 1 types, 9 molecules

#5: Sugar
ChemComp-NAG / 2-acetamido-2-deoxy-beta-D-glucopyranose / N-acetyl-beta-D-glucosamine / 2-acetamido-2-deoxy-beta-D-glucose / 2-acetamido-2-deoxy-D-glucose / 2-acetamido-2-deoxy-glucose / N-ACETYL-D-GLUCOSAMINE


Type: D-saccharide, beta linking / Mass: 221.208 Da / Num. of mol.: 9
Source method: isolated from a genetically manipulated source
Formula: C8H15NO6
IdentifierTypeProgram
DGlcpNAcbCONDENSED IUPAC CARBOHYDRATE SYMBOLGMML 1.0
N-acetyl-b-D-glucopyranosamineCOMMON NAMEGMML 1.0
b-D-GlcpNAcIUPAC CARBOHYDRATE SYMBOLPDB-CARE 1.0
GlcNAcSNFG CARBOHYDRATE SYMBOLGMML 1.0

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Non-polymers , 3 types, 27 molecules

#6: Chemical...
ChemComp-CA / CALCIUM ION


Mass: 40.078 Da / Num. of mol.: 23 / Source method: obtained synthetically / Formula: Ca
#7: Chemical ChemComp-HEM / PROTOPORPHYRIN IX CONTAINING FE / HEME


Mass: 616.487 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: C34H32FeN4O4 / Feature type: SUBJECT OF INVESTIGATION
#8: Chemical ChemComp-OXY / OXYGEN MOLECULE


Mass: 31.999 Da / Num. of mol.: 2 / Source method: obtained synthetically / Formula: O2 / Feature type: SUBJECT OF INVESTIGATION

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Details

Has ligand of interestY
Has protein modificationY

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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: CD163/Hp(1-1)Hb complex / Type: COMPLEX / Entity ID: #4 / Source: NATURAL
Molecular weightValue: 0.53 MDa / Experimental value: YES
Source (natural)Organism: Homo sapiens (human)
Buffer solutionpH: 7.5
SpecimenConc.: 0.1 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
Specimen supportGrid material: COPPER / 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: 277 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 defocus max: 2400 nm / Nominal defocus min: 900 nm
Image recordingElectron dose: 40.6 e/Å2 / Film or detector model: FEI FALCON IV (4k x 4k)
EM imaging opticsEnergyfilter name: TFS Selectris / Energyfilter slit width: 10 eV

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Processing

EM software
IDNameVersionCategory
1Topazparticle selection
2EPU3.15image acquisition
4cryoSPARC4.4.1CTF correction
9cryoSPARC4.4.1initial Euler assignment
10cryoSPARC4.4.1final Euler assignment
12cryoSPARC4.4.13D reconstruction
13PHENIXmodel refinement
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
Particle selectionNum. of particles selected: 2709108
3D reconstructionResolution: 3.3 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 245961 / Symmetry type: POINT
RefinementHighest resolution: 3.3 Å
Stereochemistry target values: REAL-SPACE (WEIGHTED MAP SUM AT ATOM CENTERS)
Refine LS restraints
Refine-IDTypeDev idealNumber
ELECTRON MICROSCOPYf_bond_d0.00224554
ELECTRON MICROSCOPYf_angle_d0.49733301
ELECTRON MICROSCOPYf_dihedral_angle_d6.7643591
ELECTRON MICROSCOPYf_chiral_restr0.0413535
ELECTRON MICROSCOPYf_plane_restr0.0034339

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