FIG. 4.

Glrx catalysis. (A) Dithiol and monothiol catalytic mechanisms of Glrx. Glrx was modeled by using the deposited PDB NMR structure 1GRX of Escherichia coli with bound glutathione (arrow) (191) and the Java web plugin Protein workshop (128). The ball-and-stick model depicts glutathione bound to Glrx via its specific GSH-binding groove. (B) The evolutionarily highly conserved function of Glrx3 (cytoplasm) and Glrx5 (mitochondria) in the maintenance and regulation of intracellular iron homeostasis. Glrx3 forms an iron-GSH complex as an intermediate to load specific cytoplasmic proteins with iron-sulfur clusters [2Fe-2S] aided by the highly conserved BolA (DNA-binding transcriptional regulator). The interaction results in various protein-iron-sulfur complexes that may or may not involve BolA or Glrx3. These complexes serve as iron storage depots or mediate cellular stress responses. Color images are available online.