Evidence for an additional disulfide reduction pathway in Escherichia coli

An Escherichia coli cell-free protein synthesis cell extract has been created that lacks all known cytoplasmic disulfide reduction pathways but still retains significant reductase activity. Oxidized glutathione was partially stabilized by deleting the gene for glutathione reductase. To avoid previously reported AhpC mutations, thioredoxin reductase was only removed after extract preparation. The trxB gene was extended to encode a hemagglutinin tag so that TrxB could be removed by affinity adsorption. However, significant glutathione reductase activity remained. The unknown glutathione reductase pathway is disabled by iodoacetamide, is inhibited by NADH, and appears to use NADPH as an electron source.