Membrane assembly of lactose permease of Escherichia coli.
Lactose permease, the lacY gene product in Escherichia coli, is an integral membrane protein. Its induction was examined in secAts and secYts mutants by measuring o-nitrophenyl-beta-galactoside uptake activity. In contrast to the synthesis of the maltose binding protein, the malE gene product, which is dependent on the secA and secY gene products, lactose permease seemed to be produced and integrated functionally into membrane independently of SecA or SecY. Gene fusion of the lamB signal sequence to the N-terminal part of the lactose permease gene resulted in production of active fused permease in the E. coli membrane. The signal sequence did not seem to be processed, judging from its mobility on SDS polyacrylamide gel electrophoresis. E. coli cell growth was super-sensitive to induction of production of the fused permease with the signal sequence in contrast to induction of the normal lactose permease. These results are consistent with the above observation that production and integration of LacY protein into membrane is relatively independent of the SecY protein that may have a certain specificity for the signal sequence or, more generally, membrane translocation intermediates.
Yamato
I
I
Department of Biological Sciences and Technology, Science University of Tokyo, Chiba.
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport; D002455:Cell Division / Q000502:physiology; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D007785:Lactose / Q000493:pharmacokinetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D018272:Porins; D021382:Protein Sorting Signals / Q000235:genetics; D011991:Receptors, Virus / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D027981:Symporters
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D018272:Porins; D021382:Protein Sorting Signals; D011991:Receptors, Virus; D011993:Recombinant Fusion Proteins; D027981:Symporters; C016532:maltoporins; C021499:lactose permease; D007785:Lactose