A 2ND-GENE INVOLVED IN THE FORMATION OF D ISULFIDE BONDS IN PROTEINS OF THE ESCHERICHIA-COLI PERIPLASMIC SPACE

A novel mutant of Escherichia coli was isolated whose phenotype is sim ilar to those of dsbA strains. For instance, it is unable to express p H 2.5 acid phosphatase, glucose-1-phosphatase and alkaline phosphatase in the periplasmic space. The mutation lies at min 26.2 of the linkag e map, and does not affect expression of DsbA. Addition of oxidized gl utathione to the growth medium restores the wild-type phenotype in the mutant while this is not the case in a dsbA strain. The product of th is new gene dsbX is thus actually involved in the formation of disulfi de bridges in the periplasmic space but can only operate if DsbA is fu nctional.