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La porina OmpD, proteína de membrana externa de salmonella enterica serovar typhimurium, participa en la expulsión del tóxico metil viológeno desde la bacteria
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Fecha
2007
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
La caracterización de las porinas de bacterias Gram-negativas ha resultado de mucha
utilidad para la comprensión de múltiples aspectos de la fisiología bacteriana. Estas
proteínas son canales acuosos que permiten la difusión pasiva de solutos hidrofilicos,
sean éstos nutrientes · o tóxicos antibacterianos. Esta característica explica en parte la
propiedad de estas células de desarrollarse en los más variados ambientes, el fenómeno ·
de resistencia a drogas, así como también aspectos de su patogenicidad en células del
hospedero. Estudios pioneros con las porinas OmpF, OmpC, PhoE y LamB fueron
llevados a cabo principalmente en Escherichia coli y en Salmonella enterica serovar
Typhimurium. De ellos ha emergido información importante acerca de la estructura y
rol de estas proteínas de membrana externa (ME) en el transporte pasivo de solutos
hacia el periplasma de la bacteria.
Evidencia genética obtenida en los últimos años sugiere que los genes ompD e
yddG serían necesarios para la resistencia de Salmonella Typhimurium al tóxico metil
viológeno (MV).· El producto del gen ompD podría actuar como un canal de ME para la
expulsión de este. En consecuencia, OmpD participaría en conjunto con la proteína de
MI YddG, fenómeno que ocurriría de forma independiente de la bomba SmvA en la
expulsión de compuestos derivados de amonio cuaternario.
Los resultados obtenidos en esta Tesis con cepas mutantes por intercambio
alélico, sugieren que SmvA es la vía primaria en la expulsión del tóxico MV y
funcionaría en una ruta diferente al sistema Y ddG-OmpD. Además, de estos
mecanismos mencionados existiría una vía dependiente de OmpW, otra porina
involucrada en el fenómeno. Otros estudios de transporte realizados in vivo con [14C]-
MV con .todas las cepas mutantes, demuestran que la proteína OmpD es un canal de
expulsión de MV.
The characterization of porins from Gram negative bacteria have become to understnd of multiple aspects of bacteria} phisiology. These porins are aqueous channels that allow passive diffusion of hydrophilic solutes, nutrients or toxins through the outer bacterial membrane. This explains in part the ability of these microorganisms to grow in severa} different environments as well as the fact drugs resistance and sorne aspects about their pathogenesis in host cells. The first studies with porins OmpF, OmpC and LamB were developing in Escherichia c;oli and Salmonella enterica serovar Typhimurium. As a result important information has been revealed about their structure and function in the passive. transport ofthe solutes towards the periplasm ofbacteria. Recent genetic evidence suggest ompD and yddG genes from Salmonella Typhimurium are required for the resistance to the toxic MV. The gene product of ompD could act as an outer membrane channel protein for the efllux of the toxic salt and would function together with the efllux pump of IM Y ddG, independently of the SmvA, other IM pump required for the efllux of quatemary ammonium compounds, including MV. In this thesis work we show that mutants strains with deletions suggest that Smv A is the main pathway used to expel MV out of the cell and would function independent of the Y ddGOmpD system. In addition an Omp W dependent pathway would exist, another porin involved in the phenomenon. Other studies that carried out in vivo transport assays using [14C]-MV and all mutants strains showed that OmpD is an outer membrane channel protein for the efflux of MV.
The characterization of porins from Gram negative bacteria have become to understnd of multiple aspects of bacteria} phisiology. These porins are aqueous channels that allow passive diffusion of hydrophilic solutes, nutrients or toxins through the outer bacterial membrane. This explains in part the ability of these microorganisms to grow in severa} different environments as well as the fact drugs resistance and sorne aspects about their pathogenesis in host cells. The first studies with porins OmpF, OmpC and LamB were developing in Escherichia c;oli and Salmonella enterica serovar Typhimurium. As a result important information has been revealed about their structure and function in the passive. transport ofthe solutes towards the periplasm ofbacteria. Recent genetic evidence suggest ompD and yddG genes from Salmonella Typhimurium are required for the resistance to the toxic MV. The gene product of ompD could act as an outer membrane channel protein for the efllux of the toxic salt and would function together with the efllux pump of IM Y ddG, independently of the SmvA, other IM pump required for the efllux of quatemary ammonium compounds, including MV. In this thesis work we show that mutants strains with deletions suggest that Smv A is the main pathway used to expel MV out of the cell and would function independent of the Y ddGOmpD system. In addition an Omp W dependent pathway would exist, another porin involved in the phenomenon. Other studies that carried out in vivo transport assays using [14C]-MV and all mutants strains showed that OmpD is an outer membrane channel protein for the efflux of MV.
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Palabras clave
Porinas, Salmonella Typhimurium