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2o8v
From Proteopedia
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PAPS reductase in a covalent complex with thioredoxin C35A
Overview
The crystal structure of Escherichia coli 3'-phosphoadenosine-5'-phosphosulfate (PAPS) reductase in complex with E. coli thioredoxin 1 (Trx1) has been determined to 3.0 A resolution. The two proteins are covalently linked via a mixed disulfide that forms during nucleophilic attack of Trx's N-terminal cysteine on the Sgamma atom of the PAPS reductase S-sulfocysteine (E-Cys-Sgamma-SO3-), a central intermediate in the catalytic cycle. For the first time in a crystal structure, residues 235-244 in the PAPS reductase C-terminus are observed, depicting an array of interprotein salt bridges between Trx and the strictly conserved glutathione-like sequence, Glu238Cys239Gly240Leu241His242. The structure also reveals a Trx-binding surface adjacent to the active site cleft and regions of PAPS reductase associated with conformational change. Interaction at this site strategically positions Trx to bind the S-sulfated C-terminus and addresses the mechanism for requisite structural rearrangement of this domain. An apparent sulfite-binding pocket at the protein-protein interface explicitly orients the S-sulfocysteine Sgamma atom for nucleophilic attack in a subsequent step. Taken together, the structure of PAPS reductase in complex with Trx highlights the large structural rearrangement required to accomplish sulfonucleotide reduction and suggests a role for Trx in catalysis beyond the paradigm of disulfide reduction.
About this Structure
2O8V is a Protein complex structure of sequences from Escherichia coli. Active as Phosphoadenylyl-sulfate reductase (thioredoxin), with EC number 1.8.4.8 Full crystallographic information is available from OCA.
Reference
3'-Phosphoadenosine-5'-phosphosulfate reductase in complex with thioredoxin: a structural snapshot in the catalytic cycle., Chartron J, Shiau C, Stout CD, Carroll KS, Biochemistry. 2007 Apr 3;46(13):3942-51. Epub 2007 Mar 13. PMID:17352498
Page seeded by OCA on Thu Feb 21 18:15:45 2008
