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The Usher N Terminus Is the Initial Targeting Site for Chaperone-Subunit Complexes and Participates in Subsequent Pilus Biogenesis Events. Tony W. Ng, 2004.Pilus biogenesis on the surface of uropathogenic Escherichia coli requires the chaperone/usher pathway, a terminal branch of the general secretory pathway . In this pathway, periplasmic chaperone-subunit complexes target an outer membrane (OM) usher for subunit assembly into pili and secretion to the cell surface . The molecular mechanisms of protein secretion across the OM are not well understood . Mutagenesis of the P pilus usher PapC and the type 1 pilus usher FimD was undertaken to elucidate the initial stages of pilus biogenesis at the OM . Deletion of residues 2 to 11 of the mature PapC N terminus abolished the targeting of the usher by chaperone-subunit complexes and rendered PapC nonfunctional for pilus biogenesis . Similarly, an intact FimD N terminus was required for chaperone-subunit binding and pilus biogenesis . Analysis of PapC-FimD chimeras and N-terminal fragments of PapC localized the chaperone-subunit targeting domain to the first 124 residues of PapC . Single alanine substitution mutations were made in this domain that blocked pilus biogenesis but did not affect targeting of chaperone-subunit complexes . Thus, the usher N terminus does not function simply as a static binding site for chaperone-subunit complexes but also participates in subsequent pilus assembly events . A Single Amino Acid Substitution Converts  -Glutamyltranspeptidase to a Class IV Cephalosporin Acylase (Glutaryl-7-Aminocephalosporanic Acid Acylase).Hideyuki Suzuki, 2004. Reconstitution of the Trimethylamine Oxide Reductase Regulatory Elements of Shewanella oneidensis in Escherichia coli. Stéphanie Gon, 2002.Several bacteria can grow by using small organic compounds such as trimethylamine oxide (TMAO) as electron acceptors . In Shewanella species, the TMAO reductase respiratory system is encoded by the torECAD operon . We showed that production of the TMAO reductase of S . oneidensis was induced by TMAO and repressed by oxygen, and we noticed that a three-gene cluster (torSTR) encoding a complex two-component regulatory system was present downstream of the torECAD operon . We introduced the torSTR gene cluster into Escherichia coli and showed that this regulatory gene cluster is involved in TMAO induction of the torE promoter but plays no role in the oxygen control . The TorR response regulator was purified, and gel shift and footprinting experiments revealed that TorR binds to a single region located about 70 bases upstream of the transcription start site of the tor structural operon . By deletion analysis, we confirmed that the TorR operator site is required for induction of the tor structural promoter . As the TMAO regulatory system of S . oneidensis is homologous to that of E . coli, we investigated a possible complementation between the TMAO regulatory components of the two bacteria . Interestingly, TorSec, the TMAO sensor of E . coli, was able to transphosphorylate TorRso, the TMAO response regulator of S . oneidensis . Characterization of the Initial Reactions during the Cometabolic Oxidation of Methyl tert-Butyl Ether by Propane-Grown Mycobacterium vaccae JOB5. Christy A. Smith, 2003.
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