Identification of a protein required for disulfide bond formation in vivo.
We describe a mutation (dsbA) that renders Escherichia coli severely defective in disulfide bond formation. In dsbA mutant cells, pulse-labeled beta-lactamase, alkaline phosphatase, and OmpA are secreted but largely lack disulfide bonds. These disulfideless proteins may represent in vivo folding intermediates, since they are protease sensitive and chase slowly into stable oxidized forms. The dsbA gene codes for a 21,000 Mr periplasmic protein containing the sequence cys-pro-his-cys, which resembles the active sites of certain disulfide oxidoreductases. The purified DsbA protein is capable of reducing the disulfide bonds of insulin, an activity that it shares with these disulfide oxidoreductases. Our results suggest that disulfide bond formation is facilitated by DsbA in vivo.
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
J C
JC
Bardwell
K
K
McGovern
J
J
Beckwith
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D001483:Base Sequence; D004220:Disulfides; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D007535:Isomerases / Q000235:genetics*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics*; D010641:Phenotype; D011487:Protein Conformation; D019704:Protein Disulfide-Isomerases; D015183:Restriction Mapping; D016415:Sequence Alignment
D001425:Bacterial Outer Membrane Proteins; D004220:Disulfides; D007328:Insulin; D010088:Oxidoreductases; D007535:Isomerases; D019704:Protein Disulfide-Isomerases