Thioredoxin

About TXN / Thioredoxin:

Thioredoxin, or TXN, for short, is a series of small redox proteins found in all organisms. They play a range of roles, including factoring into redox signaling. In humans, there are two thioredoxin proteins, encoded by the TXN and TXN2 genes. In humans, they play a key role but one that is not fully understood, in part in their response to reactive oxygen species and in cell-to-cell communication.

TXN Function
Thioredoxins are proteins that act as antioxidants. They facilitate the reduction of other proteins by cysteine thiol-disulfide exchange. TXN participates in various redox reactions through the reversible oxidation of its active center dithiol to a disulfide and catalyzes dithiol-disulfide exchange reaction. It also plays a role in the reversible S-nitrosylation of cysteine residues in target proteins and thereby contributes to the response to intracellular nitric oxide.

Thioredoxin Mechanism
Thioredoxins reduce oxidized cysteine residues and cleave disulfide bonds. In Trx1, this process begins by the attack of Cys32, one of the residues conserved in the thioredoxin CXXC motif, onto the oxidized group of the substrate.

TXN Interactions
TXN interacts with UBE2K, NFKB1, TXNIP, TXNRD1, and APEX1. TXN2 interacts with SOD1, TOMM22, TPM4, PTBP3, and POLD2.

Thioredoxin Structure
Thioredoxin is a 12-kD oxidoreductase enzyme containing a dithiol-disulfide active site. Thioredoxins are characterized at the level of their amino acid sequence by the presence of two vicinal cysteines in a CXXC motif. These two cysteines are the key to the ability of thioredoxin to reduce other proteins. Thioredoxin proteins also have a characteristic tertiary structure termed the thioredoxin fold.