SecE-dependent overproduction of SecY in Escherichia coli Evidence for interaction between two components of the secretory machinery

The secY and secE genes were individually cloned and placed under the control of the tac promoter on plasmids. Induction with isopropyl-β-D-thiogalactopyranoside resulted in the overproduction of SecE, but not that of SecY. The simultaneous induced expression of both genes in the same cells resulted in the overproduction of SecY together with that of SecE. SecY and SecE thus overproduced were localized in the cytoplasmic membrane as those expressed at the normal levels were. It is suggested that SecY and SecE interact with each other in the cytoplasmic membrane. The numbers of the SecY and SecE molecules per cell were estimated.