4ij3
Oxidoreductase Fragment of Human QSOX1 in Complex with a FAB Fragment from an Anti- Human QSOX1 Antibody
Structural highlights
FunctionQSOX1_HUMAN Catalyzes the oxidation of sulfhydryl groups in peptide and protein thiols to disulfides with the reduction of oxygen to hydrogen peroxide. May contribute to disulfide bond formation in a variety of secreted proteins. In fibroblasts, it may have tumor-suppressing capabilities being involved in growth regulation.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedQuiescin sulfhydryl oxidase 1 (QSOX1) is a catalyst of disulfide bond formation that undergoes regulated secretion from fibroblasts and is over-produced in adenocarcinomas and other cancers. We have recently shown that QSOX1 is required for incorporation of particular laminin isoforms into the extracellular matrix (ECM) of cultured fibroblasts and, as a consequence, for tumor cell adhesion to and penetration of the ECM. The known role of laminins in integrin-mediated cell survival and motility suggests that controlling QSOX1 activity may provide a novel means of combating metastatic disease. With this motivation, we developed a monoclonal antibody that inhibits the activity of human QSOX1. Here, we present the biochemical and structural characterization of this antibody and demonstrate that it is a tight-binding inhibitor that blocks one of the redox-active sites in the enzyme, but not the site at which de novo disulfides are generated catalytically. Sulfhydryl oxidase activity is thus prevented without direct binding of the sulfhydryl oxidase domain, confirming the model for the interdomain QSOX1 electron transfer mechanism originally surmised based on mutagenesis and protein dissection. In addition, we developed a single-chain variant of the antibody and show that it is a potent QSOX1 inhibitor. The QSOX1 inhibitory antibody will be a valuable tool in studying the role of ECM composition and architecture in cell migration, and the recombinant version may be further developed for potential therapeutic applications based on manipulation of the tumor microenvironment. An Inhibitory Antibody Blocks the First Step in the Dithiol/Disulfide Relay Mechanism of the Enzyme QSOX1.,Grossman I, Alon A, Ilani T, Fass D J Mol Biol. 2013 Nov 15;425(22):4366-78. doi: 10.1016/j.jmb.2013.07.011. Epub, 2013 Jul 15. PMID:23867277[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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