Examinando por Autor "Valvano, Miguel A."
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Ítem Distinct functional domains of the Salmonella enterica WbaP transferase that is involved in the initiation reaction for synthesis of the O antigen subunit(Microbiology Society, 2008-02) Saldías, M. Soledad; Patel, Kinnari; Marolda, Cristina L.; Bittner, Mauricio; Contreras, Inés; Valvano, Miguel A.WbaP is a membrane enzyme that initiates O antigen synthesis in Salmonella enterica by catalysing the transfer of galactose 1-phosphate (Gal-1-P) onto undecaprenyl phosphate (Und-P). WbaP possesses at least three predicted structural domains: an N-terminal region containing four transmembrane helices, a large central periplasmic loop, and a C-terminal domain containing the last transmembrane helix and a large cytoplasmic tail. In this work, we investigated the contribution of each region to WbaP function by constructing a series of mutant WbaP proteins and using them to complement O antigen synthesis in ΔwbaP mutants of S. enterica serovars Typhi and Typhimurium. Truncated forms of WbaP lacking the periplasmic loop exhibited altered chain-length distributions in O antigen polymerization, suggesting that this central domain is involved in modulating the chain-length distribution of the O polysaccharide. The N-terminal and periplasmic domains were dispensable for complementation of O antigen synthesis in vivo, suggesting that the C-terminal domain carries the sugar-phosphate transferase activity. However, despite the fact that they complemented the synthesis of O antigen in the ΔwbaP mutant in vivo, membrane extracts containing WbaP derivatives without the N-terminal domain failed to transfer radioactive Gal from UDP-Gal into a lipid-rich fraction. These results suggest that the N-terminal region of WbaP, which contains four transmembrane domains, is essential for the insertion or stability of the protein in the bacterial membrane. We propose that the domain structure of WbaP enables this protein not only to function in the transfer of Gal-1-P to Und-P but also to establish critical interactions with additional proteins required for the correct assembly of O antigen in S. enterica. © 2008 SGM.Ítem The Transcription Factor ArcA Modulates Salmonella’s Metabolism in Response to Neutrophil Hypochlorous Acid-Mediated Stress(Frontiers Media S.A., 2019-12) Pardo-Esté, Coral; Castro-Severyn, Juan; I. Krüger, Gabriel; Cabezas, Carolina Elizabeth; Briones, Alan Cristóbal; Aguirre, Camila; Morales, Naiyulin; Baquedano, Maria Soledad; Sulbaran, Yoelvis Noe; Hidalgo, Alejandro A.; Meneses, Claudio; Poblete-Castro, Ignacio; Castro-Nallar, Eduardo; Valvano, Miguel A.; Saavedra, Claudia P.Salmonella Typhimurium, a bacterial pathogen with high metabolic plasticity, can adapt to different environmental conditions; these traits enhance its virulence by enabling bacterial survival. Neutrophils play important roles in the innate immune response, including the production of microbicidal reactive oxygen species (ROS). In addition, the myeloperoxidase in neutrophils catalyzes the formation of hypochlorous acid (HOCl), a highly toxic molecule that reacts with essential biomolecules, causing oxidative damage including lipid peroxidation and protein carbonylation. The bacterial response regulator ArcA regulates adaptive responses to oxygen levels and influences the survival of Salmonella inside phagocytic cells. Here, we demonstrate by whole transcriptomic analyses that ArcA regulates genes related to various metabolic pathways, enabling bacterial survival during HOCl-stress in vitro. Also, inside neutrophils, ArcA controls the transcription of several metabolic pathways by downregulating the expression of genes related to fatty acid degradation, lysine degradation, and arginine, proline, pyruvate, and propanoate metabolism. ArcA also upregulates genes encoding components of the oxidative pathway. These results underscore the importance of ArcA in ATP generation inside the neutrophil phagosome and its participation in bacterial metabolic adaptations during HOCl stress. © Copyright © 2019 Pardo-Esté, Castro-Severyn, Krüger, Cabezas, Briones, Aguirre, Morales, Baquedano, Sulbaran, Hidalgo, Meneses, Poblete-Castro, Castro-Nallar, Valvano and Saavedra.