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PDBsum entry 1e4j
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Immune system
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PDB id
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1e4j
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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The 3.2-A crystal structure of the human igg1 fc fragment-Fc gammariii complex.
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Authors
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P.Sondermann,
R.Huber,
V.Oosthuizen,
U.Jacob.
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Ref.
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Nature, 2000,
406,
267-273.
[DOI no: ]
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PubMed id
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Abstract
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The immune response depends on the binding of opsonized antigens to cellular Fc
receptors and the subsequent initiation of various cellular effector functions
of the immune system. Here we describe the crystal structures of a soluble Fc
gamma receptor (sFc gammaRIII, CD16), an Fc fragment from human IgG1 (hFc1) and
their complex. In the 1:1 complex the receptor binds to the two halves of the Fc
fragment in contact with residues of the C gamma2 domains and the hinge region.
Upon complex formation the angle between the two sFc gammaRIII domains increases
significantly and the Fc fragment opens asymmetrically. The high degree of amino
acid conservation between sFc gammaRIII and other Fc receptors, and similarly
between hFc1 and related immunoglobulins, suggest similar structures and modes
of association. Thus the described structure is a model for immune complex
recognition and helps to explain the vastly differing affinities of other Fc
gammaR-IgG complexes and the Fc epsilonRI alpha-IgE complex.
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Figure 1.
Figure 1: The overall structure of the sFc bold gamma- RIII-hFc1
complex. a, Stereo ribbon representation with the dimer axis
of hFc1 (red and blue) orientated vertically. The 'proline
sandwich' consisting of Pro 329 of the C  2-A
domain and Trp 87 and Trp 110 of sFc RIII
(green) is shown in ball and stick together with the
carbohydrate residues of the Fc fragment and the interchain
disulphide bridge (yellow) of the Cys 229 residues. The
potential N-glycosylation sites in sFc RIII
are shown as cyan balls. b, Side view of the complex obtained by
a rotation of 90° around the y axis. Unless indicated, all
figures were produced with the programs MOLSCRIPT46 and
RASTER3D^47.
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Figure 2.
Figure 2: Superposition of the complexed components with the
free structures (C alpha- trace).
a, sFc RIII
in complexed form (cyan) was superimposed with a least square
algorithm using the C  atoms
of the first domain onto the structure of sFc RIII
obtained from sFc RIII
crystals (magenta). Trp 95 and Tyr 14 which form a new hydrogen
bond upon complex formation are shown in ball and stick
representation b, Overlay of the hFc1 structures obtained from
the complex (cyan) and from hFc1 crystals (magenta). For the
superposition the C atoms
of both C 3
domains were used. The orientation of the structures is the same
as in Fig. 1a.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2000,
406,
267-273)
copyright 2000.
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