In vivo oxidative protein folding can be facilitated by oxidation-reduction cycling.
Current dogma dictates that bacterial proteins with misoxidized disulfide bonds are shuffled into correctly oxidized states by DsbC. There are two proposed mechanisms for DsbC activity. The first involves a DsbC-only model of substrate disulfide rearrangement. The second invokes cycles of reduction and oxidation of substrate disulfide bonds by DsbC and DsbA respectively. Here, we addressed whether the second mechanism is important in vivo by identifying whether a periplasmic reductase could complement DsbC. We screened for naturally occurring periplasmic reductases in Bacteroides fragilis, a bacterium chosen because we predicted it encodes reductases and has a reducing periplasm. We found that the B. fragilis periplasmic protein TrxP has a thioredoxin fold with an extended N-terminal region; that it is a very active reductase but a poor isomerase; and that it fully complements dsbC. These results provide direct in vivo evidence that correctly folded protein is achievable via cycles of oxidation and reduction.
Shouldice
Stephen R
SR
Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld 4072, Australia.
Cho
Seung-Hyun
SH
Boyd
Dana
D
Heras
Begoña
B
Eser
Markus
M
Beckwith
Jon
J
Riggs
Paul
P
Martin
Jennifer L
JL
Berkmen
Mehmet
M
D001441:Bacteroides fragilis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008954:Models, Biological; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary
D004220:Disulfides; D029968:Escherichia coli Proteins; D033903:Periplasmic Proteins; D010088:Oxidoreductases; D019704:Protein Disulfide-Isomerases; C526649:dsbC protein, E coli