A colicin M derivative containing the lipoprotein signal sequence is secreted and renders the colicin M target accessible from inside the cells.
Colicin M is only released in very low amounts by cells harbouring this plasmid encoded colicin, due to the lack of a release (lysis) protein. A fusion gene (lpp'cma) was constructed which determined two proteins: Lpp'-Cma composed of the signal sequence of the murein lipoprotein (Lpp) and colicin M (Cma), and unaltered colicin M. Cells expressing the fusion gene released 50% of the total colicin M into the culture medium, compared to 1% found in the medium of cells synthesizing only colicin M. The release resulted from partial cell lysis caused by colicin M since a colicin M tolerant strain remained unaffected. Lpp'-Cma thus mimics phenotypically the action of colicin release proteins but displays a different lysis mechanism. In strains defective in components of the colicin M uptake system, Lpp'-Cma caused lysis as effectively as in uptake proficient strains. Apparently, Lpp'-Cma renders the colicin M target site accessible from inside the cell which stands in contrast to the action of colicin M which is only bactericidal when provided from outside.
Olschläger
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Mikrobiologie II, Universität Tübingen, Federal Republic of Germany.
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003087:Colicins / Q000096:biosynthesis* / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005822:Genetic Vectors; D008074:Lipoproteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids; D021382:Protein Sorting Signals / Q000032:analysis*
D003087:Colicins; D004269:DNA, Bacterial; D008074:Lipoproteins; D021382:Protein Sorting Signals