2r0k

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spinqualitylabelsall models 2r0k, resolution 3.51Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Protease domain of HGFA with inhibitor Fab58

Overview

To better understand how the relatively flat antigen-combining sites of, antibodies interact with the concave shaped substrate-binding clefts of, proteases, we determined the structures of two antibodies in complex with, the trypsin-like hepatocyte growth-factor activator (HGFA). The two, inhibitory antibodies, Ab58 and Ab75, were generated from a human Fab, phage display library with synthetic diversity in the three, complementarity determining regions (H1, H2, and H3) of the heavy chain, mimicking the natural diversity of the human Ig repertoire. Biochemical, studies and the structures of the Fab58:HGFA (3.5-A resolution) and the, Fab75:HGFA (2.2-A resolution) complexes revealed that Ab58 obstructed, substrate access to the active site, whereas Ab75 allosterically inhibited, substrate hydrolysis. In both cases, the antibodies interacted with the, same protruding element (99-loop), which forms part of the, substrate-binding cleft. Ab58 inserted its H1 and H2 loops in the cleft to, occupy important substrate interaction sites (S3 and S2). In contrast, Ab75 bound at the backside of the cleft to a region corresponding to, thrombin exosite II, which is known to interact with allosteric effector, molecules. In agreement with the structural analysis, binding assays with, active site inhibitors and enzymatic assays showed that Ab58 is a, competitive inhibitor, and Ab75 is a partial competitive inhibitor. These, results provide structural insight into antibody-mediated protease, inhibition. They suggest that unlike canonical inhibitors, antibodies may, preferentially target protruding loops at the rim of the substrate-binding, cleft to interfere with the catalytic machinery of proteases without, requiring long insertion loops.

About this Structure

2R0K is a Single protein structure of sequence from [1] and Homo sapiens. Full crystallographic information is available from OCA.

Reference

Structural insight into distinct mechanisms of protease inhibition by antibodies., Wu Y, Eigenbrot C, Liang WC, Stawicki S, Shia S, Fan B, Ganesan R, Lipari MT, Kirchhofer D, Proc Natl Acad Sci U S A. 2007 Dec 11;104(50):19784-9. Epub 2007 Dec 5. PMID:18077410 [[Category: ]]

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