The role of glutathione in periplasmic redox homeostasis and oxidative protein folding in Escherichia coli

Abstract

The thiol redox balance in the periplasm of E. coli depends on the DsbA/B pair for oxidative 14 power and the DsbC/D system as its complement for isomerization of non-native disulfides. 15 While the standard redox potentials of those systems are known, the in vivo redox potential 16 imposed onto protein thiol disulfide pairs in the periplasm remains unknown. Here, we used 17 genetically encoded redox probes (roGFP2 and roGFP-iL), targeted to the periplasm, to 18 directly probe the thiol redox homeostasis in this compartment. These probes contain two 19 cysteine residues, that are virtually completely reduced in the cytoplasm, but once exported 20 into the periplasm, can form a disulfide bond, a process that can be monitored by fluorescence 21 spectroscopy.