Proteinase sensitivity of bacteriophage lambda tail proteins gpJ and pH in complexes with the lambda receptor.

Previous studies have shown that bacteriophage lambda initially binds to liposomes bearing its receptor protein by the tip of the tail fiber (type 1 complex). It then associates more directly so that the hollow tail tube is in direct contact with the membrane (type 2 complex). DNA can be injected across the lipid bilayer into the liposome from type 2 complexes. We show here that gpJ, the tail fiber protein, becomes more sensitive to proteolytic degradation in type 2 complexes, indicating that the tail fiber does not pass into the liposome and that the tail fiber may undergo a conformational change in type 2 complexes. Another bacteriophage protein, pH, is sensitive to proteolytic degradation in free bacteriophage, type 1 complexes, or type 2 complexes formed with free receptor, but is resistant to proteinases in type 2 complexes formed with liposomes. This finding suggests that pH associates with the membrane. We suggest that this association is part of the mechanism by which a transmembrane hole for DNA entry is formed.