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Two-stage model for integration of the lysis protein E of ΦX174 into the cell envelope of Escherichia coli
Authors:Petra Schö  n,Gerald Schrot,Gerhard Wanner,Werner Lubitz,Angela Witte
Affiliation:Institute of Microbiology and Genetics, University of Vienna, Dr. Bohr Gasse 9, A-1030 Vienna, Austria;Institute of Botany, LM University of Munich, Menzingerstr. 67, D-80638 Munich, Germany
Abstract:Abstract: As a tool for determining the topology of the small, 91-amino acid ΦX174 lysis protein E within the envelope complex of Escherichia coli , a lysis active fusion of protein E with streptavidin (E-FXa-StrpA) was used. The E-FXa-StrpA fusion protein was visualised using immune electron microscopy with gold-conjugated anti-streptavidin antibodies within the envelope complex in different orientations. At the distinct areas of lysis characteristic for protein E, the C-terminal end of the fusion protein was detected at the surface of the outer membrane, whereas at other areas the C-terminal portion of the protein was located at the cytoplasmic side of the inner membrane. These results suggest that a conformational change of protein E is necessary to induce the lysis process, an assumption supported by proteinase K protection studies. The immune electron microscopic data and the proteinase K accessibility studies of the E-FXa-StrA fusion protein were used for the working model of the E-mediated lysis divided into three phases: phase 1 is characterised by integration of protein E into the inner membrane without a cytoplasmic status in a conformation with its C-terminal part facing the cytoplasmic side; phase 2 is characterised by a conformational change of the protein transferring the C-terminus across the inner membrane; phase 3 is characterised by a fusion of the inner and outer membranes and is associated with a transfer of the C-terminal domain of protein E towards the surface of the outer membrane of E. coli.
Keywords:ΦX174 lysis protein E    Integration    Escherichia coli    Conformational change of membrane protein
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