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- EMDB-49215: Local map of the CD163/Hp(1-1)Hb complex (Map H) -

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Basic information

Entry
Database: EMDB / ID: EMD-49215
TitleLocal map of the CD163/Hp(1-1)Hb complex (Map H)
Map data
Sample
  • Complex: CD163/Hp(1-1)Hb complex
KeywordsCD163 / M130 / Scavenger receptor / Haptoglobin / Hemoglobin / Hb / Hp / HpHb / Hp(1-1)Hb / hemolysis / ENDOCYTOSIS
Biological speciesHomo sapiens (human)
Methodsingle particle reconstruction / cryo EM / Resolution: 3.3 Å
AuthorsHuang C-S / White JBR / Degtjarik O
Funding support United Kingdom, 2 items
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, 2025-
Header (metadata) releaseJun 18, 2025-
Map releaseJun 18, 2025-
UpdateJul 23, 2025-
Current statusJul 23, 2025Processing site: RCSB / Status: Released

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Structure visualization

Supplemental images

Downloads & links

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Map

FileDownload / File: emd_49215.map.gz / Format: CCP4 / Size: 244.1 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
Projections & slices

Image control

Size
Brightness
Contrast
Others
AxesZ (Sec.)Y (Row.)X (Col.)
1.11 Å/pix.
x 400 pix.
= 444. Å
1.11 Å/pix.
x 400 pix.
= 444. Å
1.11 Å/pix.
x 400 pix.
= 444. Å

Surface

Projections

Slices (1/3)

Slices (1/2)

Slices (2/3)

Images are generated by Spider.

Voxel sizeX=Y=Z: 1.11 Å
Density
Contour LevelBy AUTHOR: 0.8
Minimum - Maximum-5.6168323 - 7.640699
Average (Standard dev.)-0.0015944099 (±0.049973436)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions400400400
Spacing400400400
CellA=B=C: 444.0 Å
α=β=γ: 90.0 °

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Supplemental data

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Mask #1

Fileemd_49215_msk_1.map
Projections & Slices
AxesZYX

Projections

Slices (1/2)
Density Histograms

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Half map: #2

Fileemd_49215_half_map_1.map
Projections & Slices
AxesZYX

Projections

Slices (1/2)
Density Histograms

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Half map: #1

Fileemd_49215_half_map_2.map
Projections & Slices
AxesZYX

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Density Histograms

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Sample components

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Entire : CD163/Hp(1-1)Hb complex

EntireName: CD163/Hp(1-1)Hb complex
Components
  • Complex: CD163/Hp(1-1)Hb complex

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Supramolecule #1: CD163/Hp(1-1)Hb complex

SupramoleculeName: CD163/Hp(1-1)Hb complex / type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#9
Source (natural)Organism: Homo sapiens (human)
Molecular weightTheoretical: 530 KDa

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Experimental details

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Structure determination

Methodcryo EM
Processingsingle particle reconstruction
Aggregation stateparticle

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Sample preparation

Concentration0.1 mg/mL
BufferpH: 7.5
VitrificationCryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV

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Electron microscopy

MicroscopeTFS KRIOS
Specialist opticsEnergy filter - Name: TFS Selectris / Energy filter - Slit width: 10 eV
Image recordingFilm or detector model: FEI FALCON IV (4k x 4k) / Average electron dose: 40.6 e/Å2
Electron beamAcceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron opticsIllumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Nominal defocus max: 2.4 µm / Nominal defocus min: 0.9 µm
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company

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Image processing

Particle selectionNumber selected: 2709108
CTF correctionSoftware - Name: cryoSPARC (ver. 4.4.1) / Type: PHASE FLIPPING AND AMPLITUDE CORRECTION
Startup modelType of model: NONE
Final reconstructionResolution.type: BY AUTHOR / Resolution: 3.3 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 4.4.1) / Number images used: 245961
Initial angle assignmentType: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC (ver. 4.4.1)
Final angle assignmentType: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC (ver. 4.4.1)
FSC plot (resolution estimation)

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