2fwf
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Revision as of 08:41, 21 November 2007
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high resolution crystal structure of the C-terminal domain of the electron transfer catalyst DsbD (reduced form)
Overview
Escherichia coli DsbD transports electrons from cytoplasmic thioredoxin to, periplasmic target proteins. DsbD is composed of an N-terminal (nDsbD) and, a C-terminal (cDsbD) periplasmic domain, connected by a central, transmembrane domain. Each domain possesses two cysteine residues, essential for electron transport. The transport proceeds via disulfide, exchange reactions from cytoplasmic thioredoxin to the central, transmembrane domain and via cDsbD to nDsbD, which then reduces the, periplasmic target proteins. We determined four high-resolution structures, of cDsbD: oxidized (1.65 A resolution), chemically reduced (1.3 A), photo-reduced (1.1 A) and chemically reduced at pH increased from 4.6 to, 7. The latter structure was refined at 0.99 A resolution, the highest, achieved so far for a thioredoxin superfamily member. The data reveal, unprecedented structural details of cDsbD, demonstrating that the domain, is very rigid and undergoes hardly any conformational change upon, disulfide reduction or interaction with nDsbD. In full agreement with the, crystallographic results, guanidinium chloride-induced unfolding and, refolding experiments indicate that oxidized and reduced cDsbD are equally, stable. We confirmed the structural rigidity of cDsbD by molecular, dynamics simulations. A remarkable feature of cDsbD is the pKa of 9.3 for, the active site Cys461: this value, determined using two different, experimental methods, surprisingly was around 2.5 units higher than, expected on the basis of the redox potential. Additionally, taking, advantage of the very high quality of the cDsbD structures, we carried out, pKa calculations, which gave results in agreement with the experimental, findings. In conclusion, our wide-scope analysis of cDsbD, encompassing, atomic-resolution crystallography, computational chemistry and biophysical, measurements, highlighted two so far unrecognized key aspects of this, domain: its unusual redox properties and extreme rigidity. Both are likely, to be correlated to the role of cDsbD as a covalently linked electron, shuttle between the membrane domain and the N-terminal periplasmic domain, of DsbD.
About this Structure
2FWF is a Single protein structure of sequence from Escherichia coli with IOD and NA as ligands. Active as Protein-disulfide reductase, with EC number 1.8.1.8 Full crystallographic information is available from OCA.
Reference
High-resolution structures of Escherichia coli cDsbD in different redox states: A combined crystallographic, biochemical and computational study., Stirnimann CU, Rozhkova A, Grauschopf U, Bockmann RA, Glockshuber R, Capitani G, Grutter MG, J Mol Biol. 2006 May 5;358(3):829-45. Epub 2006 Feb 28. PMID:16545842
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