Complementation of DsbA deficiency with secreted thioredoxin variants reveals the crucial role of an efficient dithiol oxidant for catalyzed protein folding in the bacterial periplasm
S. Jonda et al., Complementation of DsbA deficiency with secreted thioredoxin variants reveals the crucial role of an efficient dithiol oxidant for catalyzed protein folding in the bacterial periplasm, EMBO J, 18(12), 1999, pp. 3271-3281
The thiol/disulfide oxidoreductase DsbA is the strongest oxidant of the thi
oredoxin superfamily and is required for efficient disulfide bond formation
in the periplasm of Escherichia coli. To determine the importance of the r
edox potential of the final oxidant in periplasmic protein folding, we have
investigated the ability of the most reducing thiol/disulfide oxidoreducta
se, E. coli thioredoxin, of complementing DsbA deficiency when secreted to
the periplasm. In addition, we secreted thioredoxin variants with increased
redox potentials as well as the catalytic a-domain of human protein disulf
ide isomerase (PDI) to the periplasm, While secreted wild-type thioredoxin
and the most reducing thioredoxin variant could not replace DsbA, all more
oxidizing thioredoxin variants as well as the PDI a-domain could complement
DsbA deficiency in a DsbB-dependent manner There is an excellent agreement
between the activity of the secreted thioredoxin variants in vivo and thei
r ability to oxidize polypeptides fast and quantitatively in vitro. We conc
lude that the redox potential of the direct oxidant of folding proteins and
in particular its reactivity towards reduced polypeptides are crucial for
efficient oxidative protein folding in the bacterial periplasm.