Evidence for membrane-bound oligomerization of bacteriophage phi X174 lysis protein-E

The expression of cloned bacteriophage phi X174 lysis gene E was analyzed in minicells of Escherichia coli using two-dimensional gel electrophoresis. Beside the 10-11-kDa protein-E, at least two additional protein bands were detected, associated with the inner membrane, which showed the same isoelectric point as E. To clarify whether these proteins were E-specific, two different antibodies directed against a beta-galactosidase-E' hybrid protein and a synthetic oligopeptide corresponding to the C-terminal end of protein-E were raised. Immunoadsorption studies with anti-peptide-specific antibodies resulted in the detection of protein-E as well as in the detection of proteins of higher molecular weight. Two of these protein bands were positively recognized by anti beta-galactosidase-E' antibodies. The latter protein bands had the same molecular weight as the putative protein-E bands detected by two-dimensional gel electrophoresis indicating that these bands represent protein-E-specific oligomers. These data support the idea that an E-specific oligomeric structure penetrating the inner and outer membrane of E. coli is formed during the lytic action of protein-E.