Thioredoxin and related proteins in procaryotes

摘要: Thioredoxin is a small (Mr 12,000) ubiquitous redox protein with the conserved active site structure: -Trp-Cys-Gly-Pro-Cys-. The oxidized form (Trx-S2) contains disulfide bridge which reduced by NADPH and thioredoxin reductase; [Trx(SH)2] powerful oxidoreductase. Thioredoxins have been characterized in wide variety of prokaryotic cells, generally show about 50% amino acid homology to Escherichia coli known three-dimensional structure. In vitro Trx-(SH)2 serves as hydrogen donor for ribonucleotide reductase, an essential enzyme DNA synthesis, enzymes reducing sulfate or methionine sulfoxide. E. phage T7 replication subunit polymerase also assembly filamentous phages f1 M13 perhaps through its localization at cellular plasma membrane. Some photosynthetic organisms reduce Trx-S2 light ferrodoxin; used reductase regulate activity thiol control. Thioredoxin-negative mutants (trxA) are viable making precise physiological functions unknown. Another protein, glutaredoxin, enables GSH be PAPS reductase. Further experiments molecular genetic techniques required define relative roles glutaredoxin systems intracellular reactions.