Structural basis for target protein recognition by the protein disulfide reductase thioredoxin.
Thioredoxin is ubiquitous and regulates various target proteins through disulfide bond reduction. We report the structure of thioredoxin (HvTrxh2 from barley) in a reaction intermediate complex with a protein substrate, barley alpha-amylase/subtilisin inhibitor (BASI). The crystal structure of this mixed disulfide shows a conserved hydrophobic motif in thioredoxin interacting with a sequence of residues from BASI through van der Waals contacts and backbone-backbone hydrogen bonds. The observed structural complementarity suggests that the recognition of features around protein disulfides plays a major role in the specificity and protein disulfide reductase activity of thioredoxin. This novel insight into the function of thioredoxin constitutes a basis for comprehensive understanding of its biological role. Moreover, comparison with structurally related proteins shows that thioredoxin shares a mechanism with glutaredoxin and glutathione transferase for correctly positioning substrate cysteine residues at the catalytic groups but possesses a unique structural element that allows recognition of protein disulfides.
Maeda
Kenji
K
Enzyme and Protein Chemistry, BioCentrum-DTU, Søltofts Plads, Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Hägglund
Per
P
Finnie
Christine
C
Svensson
Birte
B
Henriksen
Anette
A
D020816:Amino Acid Motifs; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D054477:Glutaredoxins; D005978:Glutathione / Q000737:chemistry; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism; D001467:Hordeum; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D010088:Oxidoreductases / Q000737:chemistry; D011490:Protein Disulfide Reductase (Glutathione) / Q000737:chemistry*; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry; D013879:Thioredoxins / Q000737:chemistry*
D004220:Disulfides; D054477:Glutaredoxins; D011506:Proteins; D013879:Thioredoxins; D010088:Oxidoreductases; D011490:Protein Disulfide Reductase (Glutathione); D005982:Glutathione Transferase; D005978:Glutathione; D003545:Cysteine