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Abstract:
Specific localization of the lysis (L) protein of bacteriophage MS2 in the cell wall of Escherichia coli was determined by immunoelectron microscopy. After induction of the cloned lysis gene, the cells were plasmolyzed, fixed, and embedded in either Epon or Lowicryl K4M. Polyclonal L-protein-specific antiserum was purified by preabsorption to membranes from cells harboring a control plasmid. Protein A-gold was used to label the protein-antibody complexes. Between 42.8% (Lowicryl) and 33.8% (Epon) of the label was found in inner and outer membranes, but 30.3% (Lowicryl) and 32.8% (Epon) was present mostly in clusters in the adhesion sites visible after plasmolysis. The remaining label (26.9 and 33.4%, respectively) appeared to be present in the periplasmic space but may also have been part of membrane junctions not visible because of poor contrast of the specimen. In contrast, a quite different distribution of the L protein was found in cells grown under conditions of penicillin tolerance, i.e., at pH 5, a condition that had previously been shown to protect cells from L-protein-induced lysis. At tolerant conditions, only 21.0% of the L protein was in the adhesion sites; most of the protein (68.2%) was found in inner and outer membranes. It is concluded that lysis of the host, E. coli, was a result of the formation of specific L-protein-mediated membrane adhesion sites.
