2B39

Structure of mammalian C3 with an intact thioester at 3A resolution


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.00 Å
  • R-Value Free: 0.286 
  • R-Value Work: 0.278 
  • R-Value Observed: 0.289 

wwPDB Validation   3D Report Full Report



Literature

The structure of bovine complement component 3 reveals the basis for thioester function.

Fredslund, F.Jenner, L.Husted, L.B.Nyborg, J.Andersen, G.R.Sottrup-Jensen, L.

(2006) J Mol Biol 361: 115-127

  • DOI: 10.1016/j.jmb.2006.06.009
  • Primary Citation of Related Structures:  
    2B39

  • PubMed Abstract: 
  • The third component of complement (C3) is a 190 kDa glycoprotein essential for eliciting the complement response. The protein consists of two polypeptide chains (alpha and beta) held together with a single disulfide bridge. The beta-chain is composed of ...

    The third component of complement (C3) is a 190 kDa glycoprotein essential for eliciting the complement response. The protein consists of two polypeptide chains (alpha and beta) held together with a single disulfide bridge. The beta-chain is composed of six MG domains, one of which is shared with the alpha-chain. The disulfide bridge connecting the chains is positioned in the shared MG domain. The alpha-chain consists of the anaphylatoxin domain, three MG domains, a CUB domain, an alpha(6)/alpha(6)-barrel domain and the C-terminal C345c domain. An internal thioester in the alpha-chain of C3 (present in C4 but not in C5) is cleaved during complement activation. This mediates covalent attachment of the activated C3b to immune complexes and invading microorganisms, thereby opsonizing the target. We present the structure of bovine C3 determined at 3 Angstroms resolution. The structure shows that the ester is buried deeply between the thioester domain and the properdin binding domain, in agreement with the human structure. This domain interface is broken upon activation, allowing nucleophile access. The structure of bovine C3 clearly demonstrates that the main chain around the thioester undergoes a helical transition upon activation. This rearrangement is proposed to be the basis for the high level of reactivity of the thioester group. A strictly conserved glutamate residue is suggested to function catalytically in thioester proteins. Structure-based design of inhibitors of C3 activation may target a conserved pocket between the alpha-chain and the beta-chain of C3, which appears essential for conformational changes in C3.


    Organizational Affiliation

    Department of Molecular Biology, University of Aarhus, Denmark.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
C3 AB1661Bos taurusMutation(s): 0 
Gene Names: C3
Find proteins for Q2UVX4 (Bos taurus)
Explore Q2UVX4 
Go to UniProtKB:  Q2UVX4
Protein Feature View
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  • Reference Sequence
Oligosaccharides

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Entity ID: 2
MoleculeChainsChain Length2D Diagram Glycosylation3D Interactions
beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
C, D
3 N-Glycosylation Oligosaccharides Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.00 Å
  • R-Value Free: 0.286 
  • R-Value Work: 0.278 
  • R-Value Observed: 0.289 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 254.246α = 90
b = 246.857β = 90
c = 113.346γ = 90
Software Package:
Software NamePurpose
XDSdata scaling
XDSdata reduction
CNSrefinement
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2006-06-13
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary