>TIGR01068 thioredoxin thioredoxin; InterPro: IPR005746 Thioredoxins , , , are small disulphide-containing redox proteins that have been found in all the kingdoms of living organisms. Thioredoxin serves as a general protein disulphide oxidoreductase. It interacts with a broad range of proteins by a redox mechanism based on reversible oxidation of 2 cysteine thiol groups to a disulphide, accompanied by the transfer of 2 electrons and 2 protons. The net result is the covalent interconversion of a disulphide and a dithiol. TR-S_2 + NADPH + H^+ -> TR-(SH)_2 + NADP^+ (1) trx-S_2 + TR-(SH)_2 -> trx-(SH)_2 + TR-S_2 (2) Protein-S_2 + trx-(SH)_2 -> Protein-(SH)_2 + trx-S_2 (3) In the NADPH-dependent protein disulphide reduction, thioredoxin reductase (TR) catalyses reduction of oxidised thioredoxin (trx) by NADPH using FAD and its redox-active disulphide (steps 1 and 2). Reduced thioredoxin then directly reduces the disulphide in the substrate protein (step 3) . Protein disulphide isomerase (PDI), a resident foldase of the endoplasmic recticulum, is a multi-functional protein that catalyses the formation and isomerisation of disulphide bonds during protein folding , . PDI contains 2 redox active domains, near the N- and C-termini, that are similar to thioredoxin: both contribute to disulphide isomerase activity, but are functionally non-equivalent . Interestingly, a mutant PDI, with all 4 of the active cysteines replaced by serine, displays a low but detectable level of disulphide isomerase activity . Moreover, PDI exhibits chaperone-like activity towards proteins that contain no disulphide bonds, i.e. behaving independently of its disulphide isomerase activity . A number of endoplasmic reticulum proteins that differ from the PDI major isozyme contain 2 (ERp60, ERp5) or 3 (ERp72 ) thioredoxin domains; all of them seem to be PDIs. 3D-structures have been determined for a number of thioredoxins . The molecule has a doubly-wound alternating alpha/beta fold, consisting of a 5-stranded parallel beta-sheet core, enclosed by 4 alpha-helices. The active site disulphide is located at the N-terminus of helix 2 in a short segment that is separated from the rest of the helix by a kink caused by a conserved proline. The 4-membered disulphide ring is located on the surface of the protein. A flat hydrophobic surface lies adjacent to the disulphide, which presumably facilitates interaction with other proteins. One invariant feature of all thioredoxins is a cis-proline located in a loop preceding beta-strand 4. This residue is positioned in van der Waals contact with the active site cysteines and is important both for stability and function . Thioredoxin belongs to a structural family that includes glutaredoxin, glutathione peroxidase, bacterial protein disulphide isomerase DsbA, and the N-terminal domain of glutathione transferase . Thioredoxins have a beta-alpha unit preceding the motif common to all these proteins.; GO: 0009055 electron carrier activity, 0015035 protein disulfide oxidoreductase activity, 0006662 glycerol ether metabolic process, 0045454 cell redox homeostasis.

Probab=93.71  E-value=0.087  Score=31.29  Aligned_cols=36  Identities=17%  Similarity=0.565  Sum_probs=30.3

Q ss_pred             HHHCCCCCCCEEEE--CCEE---ECCCCCHHHHHHHHHHHH
Q ss_conf             98618853657998--9899---618999999999999999
Q gi|254780477|r  191 SEDFAIDSTPVFFI--GGNL---YLGDMSEGVFSKIIDSMI  226 (232)
Q Consensus       191 ~~~~gi~gTPt~~V--nG~~---~~g~~~~~~~~~~id~ll  226 (232)
T Consensus        61 A~~ygi~SIPTl~lFK~G~~V~~~vGa~pK~~l~~~~~~~~  101 (101)
T TIGR01068        61 AAKYGIRSIPTLLLFKNGKVVDRSVGALPKAALKQLINKNL  101 (101)
T ss_pred             HHHCCCCCCCEEEEECCCEEEEEEECCCCHHHHHHHHHHHC
T ss_conf             44528540563777519825200613569799999998719