Open AccessHigh‐resolution structure of recombinant Trichomonas vaginalis thioredoxin
Author(s) -
Iulek Jorge,
Alphey Magnus S.,
Coombs Graham H.,
Westrop Gareth D.,
Hunter William N.
Publication year - 2006
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444905039946
Subject(s) - thioredoxin , cysteine , active site , recombinant dna , redox , chemistry , protein structure , amino acid , biochemistry , peptide sequence , stereochemistry , ferredoxin thioredoxin reductase , thioredoxin reductase , enzyme , organic chemistry , gene
The structure of thioredoxin from the anaerobic organism Trichomonas vaginalis ( Tv Trx) has been determined at 1.9 Å resolution. The structure is that of a typical thioredoxin: a five‐stranded β‐sheet structure with two α‐helices on either side. The active site of the protein carries a Trp‐Cys‐Gly‐Pro‐Cys motif, residues 34–38, at the N‐terminus of an α‐helix (α2). The cysteine residues in this motif form a redox‐active disulfide necessary for thioredoxin activity. With high‐resolution data available, it was possible to model numerous amino‐acid side chains in alternate conformations and this includes the redox‐active disulfide cysteine residues. The sample was initially in the oxidized state and the use of X‐rays from an intense third‐generation synchrotron source resulted in partial photoreduction of this labile redox centre. Comparisons with previously determined thioredoxin structures indicate that Tv Trx is most similar to the human homologue, although the insertion of three residues between strands β4 and β5 makes the corresponding turn longer and more flexible in Tv Trx. In addition, three significant amino‐acid differences are identified on the protein surfaces near to the active‐site Cys35. These residues may contribute to the interactions that specific thioredoxins form with their cognate physiological partners.