Studies on the export of the maltose-binding protein and the LamB protein.
Two proteins encoded in the malB locus, the maltose-binding protein and the LamB protein, are exported to the periplasm and outer membrane, respectively. Both proteins are synthesized on membrane-bound polysomes in precursor forms which contain signal sequences at their amino-termini. Proteolytic removal of the signal sequence from maltose-binding protein begins co-translationally but is nat initiated until the nascent chains have attained 80% of their final length. Approximately one-third of the molecules are processed co-translationally, the remainder being processed post-translationally. In contrast, the LamB precursor is processed almost entirely post-translationally. In neither case is it clear when the polypeptide chains are transferred through the cytoplasmic membrane. An interesting feature with as yet unknown significance is the non-uniform rate of elongation of maltose-binding protein. The export of maltose-binding protein and the lamB protein as well as that of other proteins, has been shown to require an energized membrane.
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000378:metabolism*; D010582:Bacteriophage lambda; D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D004734:Energy Metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D010441:Peptide Chain Elongation, Translational; D018272:Porins; D011991:Receptors, Virus / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; C461599:maltose transport system, E coli