Reduced Aeration Affects the Expression of the NorB Efflux Pump of Staphylococcus aureus by Posttranslational Modification of MgrA
| Autor: | David C. Hooper, Liao Chun Hsing, G Florent Taguezem, Gilles R. Bolduc, Zoe Estabrooks, Régis Villet, Que Chi Truong-Bolduc |
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| Rok vydání: | 2012 |
| Předmět: |
Regulation of gene expression
Staphylococcus aureus Proteases Articles Gene Expression Regulation Bacterial Staphylococcal Infections Biology medicine.disease_cause Microbiology Gene Expression Regulation Enzymologic Oxygen Serine Bacterial Proteins Biochemistry Transcription (biology) medicine Humans Phosphorylation Efflux Oxidoreductases Protein Processing Post-Translational Molecular Biology Psychological repression |
| Zdroj: | Journal of Bacteriology. 194:1823-1834 |
| ISSN: | 1098-5530 0021-9193 |
| DOI: | 10.1128/jb.06503-11 |
| Popis: | We previously showed that at acid pH, the transcription of norB , encoding the NorB efflux pump, increases due to a reduction in the phosphorylation level of MgrA, which in turn leads to a reduction in bacterial killing by moxifloxacin, a substrate of the NorB efflux pump. In this study, we demonstrated that reduced oxygen levels did not affect the transcript levels of mgrA but modified the dimerization of the MgrA protein, which remained mostly in its monomeric form. Under reduced aeration, we also observed a 21.7-fold increase in the norB transcript levels after 60 min of growth that contributed to a 4-fold increase in the MICs of moxifloxacin and sparfloxacin for Staphylococcus aureus RN6390. The relative proportions of MgrA in monomeric and dimeric forms were altered by treatment with H 2 O 2 , but incubation of purified MgrA with extracts of cells grown under reduced but not normal aeration prevented MgrA from being converted to its dimeric DNA-binding form. This modification was associated with cleavage of a fragment of the dimerization domain of MgrA without change in MgrA phosphorylation and an increase in transcript levels of genes encoding serine proteases in cells incubated at reduced aeration. Taken together, these data suggest that modification of MgrA by proteases underlies the reversal of its repression of norB and increased resistance to NorB substrates in response to reduced-aeration conditions, illustrating a third mechanism of posttranslational modification, in addition to oxidation and phosphorylation, that modulates the regulatory activities of MgrA. |
| Databáze: | OpenAIRE |
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