Why is DsbA such an oxidizing disulfide catalyst?
DsbA, a member of the thioredoxin family of disulfide oxidoreductases, acts in catalyzing disulfide bond formation by donating its disulfide to newly translocated proteins. We have found that the two central residues within the active site Cys-30-Pro-31-His-32-Cys-33 motif are critical in determining the exceptional oxidizing power of DsbA. Mutations that change these two residues can alter the equilibrium oxidation potential of DsbA by more than 1000-fold. A quantitative explanation for the very high redox potential of DsbA was found by measuring the pKa of a single residue, Cys-30. The pKa of Cys-30 varied dramatically from mutant to mutant and could accurately predict the oxidizing power of each DsbA mutant protein.
Universität Regensburg Institut für Biophysik und Physikalische Biochemie, Federal Republic of Germany.
U
U
Grauschopf
J R
JR
Winther
P
P
Korber
T
T
Zander
P
P
Dallinger
J C
JC
Bardwell
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism*; D004795:Enzyme Stability; D007535:Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D004220:Disulfides; D011993:Recombinant Fusion Proteins; D010088:Oxidoreductases; D001616:beta-Galactosidase; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; D003545:Cysteine