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PDBsum entry 1bfo
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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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Crystal structures of a rat anti-Cd52 (campath-1) therapeutic antibody FAB fragment and its humanized counterpart.
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Authors
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G.M.Cheetham,
G.Hale,
H.Waldmann,
A.C.Bloomer.
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Ref.
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J Mol Biol, 1998,
284,
85-99.
[DOI no: ]
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PubMed id
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Abstract
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The CAMPATH-1 family of antibodies are able systematically to lyse human
lymphocytes with human complement by targeting the small cell-surface
glycoprotein CD52, commonly called the CAMPATH-1 antigen. These antibodies have
been used clinically for several years, providing therapy for patients with a
variety of immunologically mediated diseases. We report here the first X-ray
crystallographic analyses of a Fab fragment from a rat antibody, the original
therapeutic monoclonal CAMPATH-1G and its humanized counterpart CAMPATH-1H, into
which the six complementarity-determining regions of the rat antibody have been
introduced. These structures have been refined at 2.6 A and 3.25 A resolution,
respectively. The VL domains of adjacent molecules of CAMPATH-1H form a
symmetric dimer within the crystals with an inter-molecular extended beta-sheet
as seen in light chain dimers of the kappa class. Crystals of CAMPATH-1G have
translational pseudo-symmetry. Within the antibody-combining sites, which are
dominated by the protrusion of LysH52b and LysH53 from hypervariable loop H2,
the charge distribution and overall integrity are highly conserved, but large
changes in the position of loop H1 are observed and an altered conformation of
loop H2. The major determinants of this are framework residues H71 and H24,
whose identity differs in these two antibodies. These structures provide a
detailed structural insight into the transplantation of an intact
antibody-combining site between a rodent and a human framework, and provide an
increased understanding of the specificity and antigen affinity of this pair of
CAMPATH-1 antibodies for CD52. This study forms the structural basis for future
modification and design of more effective antibodies to this important antigen.
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Figure 3.
Figure 3. The structure of the inter-molecular V[L]
-V[L]dimer seen in CAMH. A complete Fab is shown with the
V[L]and C[L]domains in green and the V[H]and C[H]domains in
yellow. In cyan is shown the V[L] domain of an adjacent molecule
at position ( -y, -x 1/6 - z), related by a vertical
crystallographic 2-fold axis lying approximately in the plane of
the paper. The side-chains ArgL18 and AspL70', which make a
symmetrical pair of salt-bridges, are labelled. There is also a
hydrogen bond between ArgL18 and SerL7'. The antiparallel
interaction between the first b-strands of the two V[L] domains,
showing the extent of the intermolecular hydrogen bonding
between residues L9-L12, viewed from the outside of the dimer
towards the interface is shown in detail (RIBBONS; [Carson
1991]).
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Figure 6.
Figure 6. The antibody-combining site. (a) The molecular
surface (drawn by the program GRASP; [Nicholl and Honig 1991])
of the CAMH antibody-combining site coloured by electrostatic
potential (blue is positive, red is negative and white is
neutral) viewed in an orientation similar to that in Figure 5(c)
and (d). (b) and (c) Atomic representations (drawn by the
program RIBBONS; [Carson 1991]) of (b) CAMH and (c) CAMG,
corresponding to approximately the same orientation as that in
(a).
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1998,
284,
85-99)
copyright 1998.
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