title: Transposon Tn10-dependent expression of the lamB gene in Escherichia coli.
abstract: Among Tn10 insertions isolated in or near the malB region of Escherichia coli, one (zjb-729::Tn10) mapped between malK and lamB or late in malK and allowed MalT-independent expression of lamB. Tn10-dependent expression of a lamB-lacZ protein fusion was 25% of the expression of the fusion from the malK-lamB operon promoter in malTc constitutive strains. The maltoporin content of a strain carrying this Tn10 was about 20% that of a malTc malB+ strain. Transport of maltose at concentrations of below 10(-6) M was reduced about threefold. When maltoporin was present at about 50% of the level of malTc malB+ strains, maltose transport was largely restored. We conclude that maltoporin is not rate limiting for maltose transport in wild-type cells but becomes rate limiting when the ratio of maltoporin to other maltose transport components is reduced more than twofold.
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D001692:Biological Transport; D002876:Chromosomes, Bacterial / Q000502:physiology; D003090:Coliphages / Q000235:genetics; D004262:DNA Restriction Enzymes; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D005796:Genes; D005798:Genes, Bacterial; D005838:Genotype; D008320:Maltose / Q000378:metabolism; D018272:Porins; D011991:Receptors, Virus / Q000235:genetics*; D013045:Species Specificity; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004251:DNA Transposable Elements; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; D008320:Maltose; D004262:DNA Restriction Enzymes; D001616:beta-Galactosidase