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PDBsum entry 1t3f
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Immune system
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PDB id
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1t3f
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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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Three-Dimensional structures of a humanized anti-Ifn-Gamma FAB (huzaf) in two crystal forms.
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Authors
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P.C.Bourne,
S.S.Terzyan,
G.Cloud,
N.F.Landolfi,
M.Vásquez,
A.B.Edmundson.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2004,
60,
1761-1769.
[DOI no: ]
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PubMed id
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Abstract
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Three-dimensional structures were determined for two crystal forms (orthorhombic
P2(1)2(1)2(1) and monoclinic C2) of the Fab from the humanized version of a
murine monoclonal antibody (AF2) that possesses binding and potent neutralizing
activity against human interferon gamma (IFN-gamma). This humanized antibody
(HuZAF; USAN name fontolizumab) is currently in phase II clinical trials for the
treatment of Crohn's disease. HuZAF exhibits binding and IFN-gamma neutralizing
capacities that closely approximate those of the original antibody. It is shown
that HuZAF, whose VH domain was designed using a best-sequence-fit approach, is
closer structurally to its mouse precursor than is a version whose VH was
constructed using a human sequence with lower homology to the original mouse
sequence. This work thus offers direct structural evidence in support of the
best-sequence-fit approach and adds to previous results of biological and
biochemical evaluations of distinctly engineered antibodies that also favored
the use of a best-sequence-fit strategy. A second crystal type appeared during
attempts to crystallize the Fab-IFN-gamma complex. The antibody-antigen complex
that existed in solution dissociated in the crystallization mixture. A
conformationally altered but unliganded HuZAF protein crystallized in a
different space group (C2), with two Fab molecules in the asymmetric unit. In
this crystal lattice, no space was available for accommodating the IFN-gamma
antigen. Thus, there are currently three slightly different structures of the
HuZAF Fab.
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Figure 2.
Figure 2
Stereo illustration of the three-dimensional structure of the HuZAF Fab, prepared with the
program MOLSCRIPT (Kraulis, 1991[174] [Kraulis, P. J. (1991). J. Appl. Cryst. 24,
946-950.]-[175][bluearr.gif] ). Secondary elements are superimposed on backbone tracings,
which are colored yellow in the L chain and steel blue in the H chain. [176][beta]
-Strands are represented by directional arrows: cyan for the four-stranded [177][beta]
-pleated sheets and magenta for the five-stranded (VL) and three-stranded layers (CL) of
the L chain and red and white for the corresponding [178][beta] -pleated sheets in the H
chain. Helices are identified by red and yellow spirals. CDRs are marked 1, 2 and 3.
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Figure 3.
Figure 3
(a) Polypeptide tracings of the VH and VL domains of the HuAF2 Fab (PDB code [187]1b4j )
in red, superimposed on those of the murine domains in the mouse-human chimeric ChiAF2 Fab
(PDB code [188]1b2w ) in white. CDRs in the HuAF2 have amino-acid sequences excerpted from
those in the original murine AF2 antibody. (b) Backbone tracings of HuZAF V domains (cyan)
overlaid on those of ChiAF2 (Maloney et al., 1997[189] [Maloney, D. G., Grillo-Lopez, A.
J., White, C. A., Bodkin, D., Schilder, R. J., Neidhart, J. A., Janakiraman, N., Foon, K.
A., Liles, T. M., Dallaire, B. K., Wey, K., Royston, I., Davis, T. & Levy, R. (1997).
Blood, 90, 2188-2195.]-[190][bluearr.gif] ). In HuZAF, the substitution of two acceptor
framework residues with mouse residues, Val11 by leucine and Arg38 by lysine,
significantly improves the structural mimicry relative to ChiAF2.
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2004,
60,
1761-1769)
copyright 2004.
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