Compact reduced thioredoxin structure from the thermophilic bacteria Thermus thermophilus

Abstract

The X-ray crystallographic structure of a thioredoxin from Thermus thermophilus was solved to 1.8 A resolution by molecular replacement. The crystals' space group was C2 with cell dimensions of a = 40.91, b = 95.44, c = 56.68 A, beta =91.41 degrees, with two molecules in the asymmetric unit. Unlike the reported thioredoxin structures, the biological unit of T. thermophilus thioredoxin is a dimer both in solution and in the crystal. The fold conforms to the "thioredoxin fold" that is common over a class of nine protein families including thioredoxin; however, the folded portion of this protein is much more compact than other thioredoxins previously solved by X-ray crystallography being reduced by one alpha-helix and one beta-strand. As with other thioredoxins, the active site is highly conserved even though the variation in sequence can be quite large. The T. thermophilus thioredoxin has some variability at the active site, especially compared with previously solved structures from bacterial sources.

Expression, purification, crystallization and preliminary X-ray diffraction analysis of mitochondrial thioredoxin Trx3 fromSaccharomyces cerevisiae

“…Calibration of the column with molecular-weight standards showed that these peaks correspond to molecular weights of 12.8, 26 and !70 kDa, respectively. This implied that Trx3 also forms dimers and multimers in solution, as reported for thioredoxins from other species (Rehse et al, 2005;Smeets et al, 2005;Friemann et al, 2003;Weichsel et al, 1996).…”

“…Recently, Trx3 has been found to have a functional relationship with GrxR1 (glutathione reductase) and an overlapping function with GSH (Trotter & Grant, 2005). A large variety of thioredoxin structures from various organisms have been determined (Rehse et al, 2005;Smeets et al, 2005;Friemann et al, 2003;Capitani et al, 2000;Weichsel et al, 1996), but the structure of human thioredoxin 2 is that of a mitochondrial Trx. Recently, the crystal structure of Trx2 from the yeast Saccharomyces cerevisiae has also been solved by our group (Bao et al, 2006).…”

Crystal structure of the yeast cytoplasmic thioredoxin Trx2

“…The general fold of Trx2 resembles thioredoxins from other sources,16–23 consisting of five mixed β‐strands flanked by four helices [Fig. 1(A)].…”

“…Compared to the human hTXN1 protein, Phe27 of Trx2 replaces a serine, and its aromatic ring protects Cys34 from the solvent. A phenylalanine is found at the same position in the thioredoxin of the thermophilic bacterium Thermus thermophilus 21…”

The Machinery for Oxidative Protein Folding in Thermophiles

“…A Trx from the thermophilic bacterium Thermus thermophilus was isolated, and its structure solved to 1.8-Å resolution (83). The folded portion of this Trx is in a more compact form than standard Trxs, although this protein contains, like other Trxs from thermophilic microorganisms, a 30-residue N-terminal extension and a significantly longer C-terminal ␣-helix.…”