Membrane insertion of the Escherichia coli MalF protein in cells with impaired secretion machinery.
The MalF protein is an integral membrane protein of Escherichia coli containing eight membrane-spanning stretches and a large periplasmic domain of approximately 180 amino acids. We have asked whether this protein is dependent for its membrane insertion on the bacterial secretion machinery specified by the sec genes. Using azide to inhibit the SecA protein and sec mutants to reduce the functioning of the machinery, we have studied the membrane assembly of MalF and beta-galactosidase and alkaline phosphatase fusions to MalF. In no case did we see an effect of reducing sec gene function on the insertion of MalF or fusion proteins. Selection for mutants that would cause internalization of a MalF-beta-galactosidase hybrid protein yielded no mutations in sec genes. Our results suggest that MalF can assemble in the membrane independently of the bacterial secretion machinery.
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
K
K
McGovern
J
J
Beckwith
D018528:ATP-Binding Cassette Transporters; D000469:Alkaline Phosphatase / Q000378:metabolism; D001386:Azides / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D010450:Endopeptidases / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D008320:Maltose; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009004:Monosaccharide Transport Proteins; D009841:Oligonucleotides / Q000737:chemistry; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D001386:Azides; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D009841:Oligonucleotides; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins; C461599:maltose transport system, E coli; D008320:Maltose; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase; D010450:Endopeptidases