The cysteine 354 and 277 residues of Salmonella enterica serovar Typhi EnvZ are determinants of autophosphorylation and OmpR phosphorylation |
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Authors: | Ricardo Oropeza,& Edmundo Calva |
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Affiliation: | Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico |
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Abstract: | An initial biochemical characterization of the Salmonella enterica serovar Typhi ( S . Typhi) EnvZ sensor protein and several mutant derivatives was performed. Autophosphorylation levels were higher for Escherichia coli EnvZ, intermediate for S. enterica serovar Typhimurium EnvZ and very low for S . Typhi EnvZ, in spite of their high amino acid sequence identity. Consequently, OmpR phosphorylation was related to EnvZ autophosphorylation. Among the mutant derivatives, a C354G mutation in S . Typhi EnvZ resulted in a substantial increase in autophosphorylation, while mutation of its other cysteine residue at position 277 to L or S decreased the EnvZ autophosphorylation level. Upon heterodimerization, the S . Typhi C354G mutant complemented the wild type in vitro , increasing the EnvZ-P yield of both monomers, in accordance with the model where EnvZ autophosphorylation occurs in trans , indicating that dimer formation is a dynamic process. Hence, the C354 and the C277 residues are fundamental in determining the particular intrinsic biochemical characteristics of EnvZ. |
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Keywords: | EnvZ OmpR signal transduction two-component systems autophosphorylation |
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