The bacterial cell membrane is involved in a variety of activities, each of which depends upon the interaction of membrane components (proteins, phospholipids, lipopolysaccharides). In sensitive cells, many of these activities are inhibited by bacteriocins whereas in bacteriocin tolerant cells they are not inhibited. The goal of research proposed is to describe, on a genetic and biochemical level, the role of individual membrane components in bacteriocin tolerance. The membrane protein to be studied is the To1G protein, missing from the outer membrane of E. coli to1G mutants. We will purify this protein, characterize the purified material chemically and use it to attempt reconstitution of bacteriocin sensitivity using to1G mutants.