3qd9 | pdb_00003qd9

C72S/C353S mutant of Trypanosoma brucei QSOX containing an interdomain disulfide

spinqualitylabelsall models 3qd9, resolution 3.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3qd9 is a 4 chain structure with sequence from Trypanosoma brucei. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: FAD Related: 3qcp Gene: QSOX, Tb927.6.1850 (Trypanosoma brucei) Activity: Thiol oxidase, with EC number 1.8.3.2 Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed Protein stability, assembly, localization and regulation often depend on the formation of disulphide crosslinks between cysteine side chains. Enzymes known as sulphydryl oxidases catalyse de novo disulphide formation and initiate intra- and intermolecular dithiol/disulphide relays to deliver the disulphides to substrate proteins. Quiescin sulphydryl oxidase (QSOX) is a unique, multi-domain disulphide catalyst that is localized primarily to the Golgi apparatus and secreted fluids and has attracted attention owing to its overproduction in tumours. In addition to its physiological importance, QSOX is a mechanistically intriguing enzyme, encompassing functions typically carried out by a series of proteins in other disulphide-formation pathways. How disulphides are relayed through the multiple redox-active sites of QSOX and whether there is a functional benefit to concatenating these sites on a single polypeptide are open questions. Here we present the first crystal structure of an intact QSOX enzyme, derived from a trypanosome parasite. Notably, sequential sites in the disulphide relay were found more than 40 A apart in this structure, too far for direct disulphide transfer. To resolve this puzzle, we trapped and crystallized an intermediate in the disulphide hand-off, which showed a 165 degrees domain rotation relative to the original structure, bringing the two active sites within disulphide-bonding distance. The comparable structure of a mammalian QSOX enzyme, also presented here, shows further biochemical features that facilitate disulphide transfer in metazoan orthologues. Finally, we quantified the contribution of concatenation to QSOX activity, providing general lessons for the understanding of multi-domain enzymes and the design of new catalytic relays. The dynamic disulphide relay of quiescin sulphydryl oxidase.,Alon A, Grossman I, Gat Y, Kodali VK, DiMaio F, Mehlman T, Haran G, Baker D, Thorpe C, Fass D Nature. 2012 Aug 16;488(7411):414-8. PMID:22801504 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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