Two-stage model for integration of the lysis protein E of phi X174 into the cell envelope of Escherichia coli.
As a tool for determining the topology of the small, 91-amino acid phi X174 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.
Schön
P
P
Institute of Microbiology and Genetics, University of Vienna, Austria.
Schrot
G
G
Wanner
G
G
Lubitz
W
W
Witte
A
A
D001433:Bacteriolysis; D010584:Bacteriophage phi X 174 / Q000378:metabolism*; D019286:Endopeptidase K; D004926:Escherichia coli / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D011487:Protein Conformation; D012697:Serine Endopeptidases / Q000494:pharmacology; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
D008565:Membrane Proteins; D014764:Viral Proteins; D012697:Serine Endopeptidases; D019286:Endopeptidase K