Release of periplasmic proteins induced in E. coli by expression of an N-terminal proximal segment of the phage fd gene 3 protein.

We used the enzymes beta-lactamase and alkaline phosphatase to quantitatively evaluate the release of periplasmic proteins from E. coli cells transformed by plasmids harboring gene 3 of phage fd. Different deletion mutants of gene 3 released varying fractions of the enzymes. From these results we conclude that essentially the amino-terminal proximal part, upstream of the first glycine-rich region but not this region itself, is responsible for the excretion of periplasmic proteins in E. coli cells expressing the gene 3 protein of phage fd.