2I07

Human Complement Component C3b


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 4.00 Å
  • R-Value Free: 0.323 
  • R-Value Work: 0.273 
  • R-Value Observed: 0.275 

wwPDB Validation   3D Report Full Report



Literature

Structure of C3b reveals conformational changes that underlie complement activity.

Janssen, B.J.Christodoulidou, A.McCarthy, A.Lambris, J.D.Gros, P.

(2006) Nature 444: 213-216

  • DOI: 10.1038/nature05172
  • Primary Citation of Related Structures:  
    2I07

  • PubMed Abstract: 
  • Resistance to infection and clearance of cell debris in mammals depend on the activation of the complement system, which is an important component of innate and adaptive immunity. Central to the complement system is the activated form of C3, called C3b, ...

    Resistance to infection and clearance of cell debris in mammals depend on the activation of the complement system, which is an important component of innate and adaptive immunity. Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces to amplify complement response, label cells for phagocytosis and stimulate the adaptive immune response. C3b consists of 1,560 amino-acid residues and has 12 domains. It binds various proteins and receptors to effect its functions. However, it is not known how C3 changes its conformation into C3b and thereby exposes its many binding sites. Here we present the crystal structure at 4-A resolution of the activated complement protein C3b and describe the conformational rearrangements of the 12 domains that take place upon proteolytic activation. In the activated form the thioester is fully exposed for covalent attachment to target surfaces and is more than 85 A away from the buried site in native C3 (ref. 5). Marked domain rearrangements in the alpha-chain present an altered molecular surface, exposing hidden and cryptic sites that are consistent with known putative binding sites of factor B and several complement regulators. The structural data indicate that the large conformational changes in the proteolytic activation and regulation of C3 take place mainly in the first conversion step, from C3 to C3b. These insights are important for the development of strategies to treat immune disorders that involve complement-mediated inflammation.


    Organizational Affiliation

    Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Complement C3b A645Homo sapiensMutation(s): 0 
Gene Names: C3CPAMD1
Find proteins for P01024 (Homo sapiens)
Explore P01024 
Go to UniProtKB:  P01024
NIH Common Fund Data Resources
PHAROS:  P01024
Protein Feature View
Expand
  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Complement C3b B915Homo sapiensMutation(s): 0 
Gene Names: C3CPAMD1
Find proteins for P01024 (Homo sapiens)
Explore P01024 
Go to UniProtKB:  P01024
NIH Common Fund Data Resources
PHAROS:  P01024
Protein Feature View
Expand
  • Reference Sequence
Oligosaccharides

Help

Entity ID: 3
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
alpha-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
C
3 N-Glycosylation Oligosaccharides Interaction
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
NAG
Query on NAG

Download Ideal Coordinates CCD File 
B
2-acetamido-2-deoxy-beta-D-glucopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 4.00 Å
  • R-Value Free: 0.323 
  • R-Value Work: 0.273 
  • R-Value Observed: 0.275 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 123.91α = 90
b = 128.537β = 90
c = 147.034γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
DNAdata collection
MOSFLMdata reduction
CCP4data scaling
PHASERphasing

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-10-24
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary