title: An Escherichia coli mutation preventing degradation of abnormal periplasmic proteins.
abstract: A fusion between tsr (encoding the inner membrane protein Tsr) and phoA (encoding the periplasmic protein alkaline phosphatase, AP) generates a membrane-bound hybrid protein (Tsr-AP 2) with AP enzymatic activity. The hybrid protein is proteolytically unstable and is broken down to yield a smaller, soluble species with AP activity. We devised a genetic screen to distinguish between cells containing only membrane-bound AP and those containing soluble AP. The screen depends on diffusion of soluble AP away from cells with a leaky outer membrane to produce a halo of AP activity around colonies on solid growth medium. Several mutants lacking this halo show reduced degradation of Tsr-AP 2. One mutant is also defective in breakdown of five other abnormal periplasmic proteins but not of two cytoplasmic proteins. The mutation in this strain, degP4::Tn5, defines a locus distinct from previously identified loci that affect protein stability or protease activities. This strain may be useful for preventing the breakdown of unstable foreign proteins in Escherichia coli.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.
authors.forename: K L
authors.initials: KL
authors.lastname: Strauch
authors.forename: J
authors.initials: J
authors.lastname: Beckwith
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D009154:Mutation; D010447:Peptide Hydrolases / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000469:Alkaline Phosphatase; D010447:Peptide Hydrolases