title: High-sensitivity detection of newly induced LamB protein on the Escherichia coli cell surface.
abstract: The kinetics of the appearance at the cell surface of the outer membrane LamB protein after induction were determined by using specific antibodies and radioiodinated protein A as a probe. This was done in two different induction systems. First, LamB protein was induced in a wild-type strain by the simultaneous addition of cyclic AMP and maltose. Second, an operon fusion strain in which the lamB gene is expressed under lac promoter control was used; in this system, LamB protein can be induced by isopropyl-beta-D-thiogalactopyranoside. When uninduced cells were grown in glucose minimal medium, background expression of the lamB gene was found to be ca. 10-fold lower in lac-lamB cells than in wild-type cells. The level of LamB protein present in uninduced wild-type cells could, however, be reduced by supplementing the growth medium with Casamino Acids. After induction, the LamB protein appeared at the cell surface of both strains within a few minutes, and then the LamB level per cell increased linearly. The time lag in cell surface exposure of LamB protein differed slightly under both induction conditions: the LamB protein appeared at the surface of lac-lamB cells within 3 min of induction, whereas in wild-type cells it could not be detected earlier than after 4 to 5 min of induction.
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D010582:Bacteriophage lambda / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004251:DNA Transposable Elements; D000939:Epitopes / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics*; D007106:Immune Sera; D007700:Kinetics; D018272:Porins; D011991:Receptors, Virus / Q000032:analysis / Q000235:genetics*; D013045:Species Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004251:DNA Transposable Elements; D000939:Epitopes; D007106:Immune Sera; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins