2o5y | pdb_00002o5y

Crystal structure of the 1E9 LeuH47Trp/ArgH100Trp Fab progesterone complex

spinqualitylabelsall models 2o5y, resolution 2.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2o5y is a 2 chain structure with sequence from Homo sapiens and Mus musculus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.85Å Ligands: SO4, STR Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Molecular recognition by the adaptive immune system relies on specific high-affinity antibody receptors that are generated from a restricted set of starting sequences through homologous recombination and somatic mutation. The steroid binding antibody DB3 and the catalytic Diels-Alderase antibody 1E9 derive from the same germ line sequences but exhibit very distinct specificities and functions. However, mutation of only two of the 36 sequence differences in the variable domains, Leu(H47)Trp and Arg(H100)Trp, converts 1E9 into a high-affinity steroid receptor with a ligand recognition profile similar to DB3. To understand how these changes switch binding specificity and function, we determined the crystal structures of the 1E9 Leu(H47)Trp/Arg(H100)Trp double mutant (1E9dm) as an unliganded Fab at 2.05 A resolution and in complex with two configurationally distinct steroids at 2.40 and 2.85 A. Surprisingly, despite the functional mimicry of DB3, 1E9dm employs a distinct steroid binding mechanism. Extensive structural rearrangements occur in the combining site, where residue H47 acts as a specificity switch and H100 adapts to different ligands. Unlike DB3, 1E9dm does not use alternative binding pockets or different sets of hydrogen-bonding interactions to bind configurationally distinct steroids. Rather, the different steroids are inserted more deeply into the 1E9dm combining site, creating more hydrophobic contacts that energetically compensate for the lack of hydrogen bonds. These findings demonstrate how subtle mutations within an existing molecular scaffold can dramatically modulate the function of immune receptors by inducing unanticipated, but compensating, mechanisms of ligand interaction. Closely related antibody receptors exploit fundamentally different strategies for steroid recognition.,Verdino P, Aldag C, Hilvert D, Wilson IA Proc Natl Acad Sci U S A. 2008 Aug 19;105(33):11725-30. Epub 2008 Aug 8. PMID:18689687 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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