Browsing by Author "Palacios, JL"

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    Cloning and comparison of ten gene sequences of a Chilean H-pylori strain with other H-pylori strains revealed higher variability for VacA and CagA virulence factors
    (2002) Müller, I; Medina-Selby, A; Palacios, JL; Martinez, P; Opazo, P; Bruce, E; Mancilla, M; Valenzuela, P; Yudelevich, A; Venegas, A
    We have cloned and sequenced ten Helicobacter pylori genes from a Chilean strain (CH-CTX1) including: a cytotoxin VacA fragment, a CagA fragment (A 17), a species-specific protein (TsaA), urease subunits (UreA, UreB), a flagellin subunit (FlaB), heat shock proteins (HspA and HspB), adhesin (HpaA) and a lipoprotein (Lpp20). We compared their deduced amino acid sequences with the corresponding sequences from three unrelated H. pylori strains, including fully sequenced strains 26695(UK) and J99(USA), and found that eight of them (UreA, UreB, FlaB, HspA, HspB, Lpp20, TsaA and HpaA) presented more than 97.3% identity. In contrast, VacA partial sequence showed lower identity values (93.2-94.9%). Moreover, we found major differences in the A] 7 region respect to the number and arrangement of the internal repeated elements when sequences from different strains were aligned. The A17 regions from strains CH-CTX1 and 26695 are very similar (91.8% identity) but lacked 6 repeated elements when compared to the Australian strains ATCC 43526 and NCTC 11637. The CCUG 17874 A17 region showed the largest deletion involving 9 repeats. A 17 size differences between strains CCUG 17874 and CH-CTX1 were verified by PCR and polypeptide size. Such differences may explain variations in virulence among H. pylori strains as well as diversity in serum immunoreactivity.
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    Subset of hybrid eukaryotic proteins is exported by the type I secretion system of Erwinia chrysanthemi
    (2001) Palacios, JL; Zaror, I; Martínez, P; Uribe, F; Opazo, P; Socías, T; Gidekel, M; Venegas, A
    Erwinia chrysanthemi exports degradative enzymes by using a type I protein secretion system. The proteases secreted by this system lack an N-terminal signal peptide but contain a C-terminal secretion signal. To explore the substrate specificity of this system, we have expressed the E. chrysanthemi transporter system (prtDEF genes) in Escherichia coli and tested the ability of this ABC transporter to export hybrid proteins carrying C-terminal fragments off. chrysanthemi protease B. The C terminus contains six glycine-rich repeated motifs, followed by two repeats of the sequences DFLV and DW. Two types of hybrid proteins were assayed for transport, proteins with the 93-residue-protease-B C terminus containing one glycine rich repeat and both hydrophobic terminal repeats and proteins with the 181-residue C terminus containing all repeat motifs, Although the shorter C terminus is unable to export the hybrids, the longer C terminus can promote the secretion of hybrid proteins with N termini as large as 424 amino acids, showing that the glycine-rich motifs are required for the efficient secretion of these hybrids. However, the secretion of hybrids occurs only if these proteins do not carry disulfide bonds in their mature structures. These latter results suggest that disulfide bond formation can occur prior to or during the secretion. Disulfide bonds may prevent type I secretion of hybrids. One simple hypothesis to explain these results is that the type I channel is too narrow to permit the export of proteins with secondary structures stabilized by disulfide bonds.