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PDBsum entry 2win
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Immune system
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PDB id
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2win
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Contents |
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638 a.a.
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901 a.a.
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507 a.a.
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84 a.a.
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References listed in PDB file
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Key reference
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Title
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Structural and functional implications of the alternative complement pathway c3 convertase stabilized by a staphylococcal inhibitor.
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Authors
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S.H.Rooijakkers,
J.Wu,
M.Ruyken,
R.Van domselaar,
K.L.Planken,
A.Tzekou,
D.Ricklin,
J.D.Lambris,
B.J.Janssen,
J.A.Van strijp,
P.Gros.
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Ref.
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Nat Immunol, 2009,
10,
721-727.
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PubMed id
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Abstract
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Activation of the complement system generates potent chemoattractants and leads
to the opsonization of cells for immune clearance. Short-lived protease
complexes cleave complement component C3 into anaphylatoxin C3a and opsonin C3b.
Here we report the crystal structure of the C3 convertase formed by C3b and the
protease fragment Bb, which was stabilized by the bacterial immune-evasion
protein SCIN. The data suggest that the proteolytic specificity and activity
depend on the formation of dimers of C3 with C3b of the convertase. SCIN blocked
the formation of a productive enzyme-substrate complex. Irreversible
dissociation of the complex of C3b and Bb is crucial to complement regulation
and was determined by slow binding kinetics of the Mg(2+)-adhesion site in Bb.
Understanding the mechanistic basis of the central complement-activation step
and microbial immune evasion strategies targeting this step will aid in the
development of complement therapeutics.
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