The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em>
In order to survive the exposure to acid pH, <em>Escherichia coli</em> activates molecular circuits leading from acid tolerance to extreme acid resistance (AR). The activation of the different circuits involves several global and specific regulators affecting the expression of membrane,...
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| Format: | Article |
| Language: | English |
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AIMS Press
2017-02-01
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| Series: | AIMS Microbiology |
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| Online Access: | http://www.aimspress.com/microbiology/article/1267/fulltext.html |
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| author | Angela Tramonti Fiorenzo De Santis Eugenia Pennacchietti Daniela De Biase |
| author_facet | Angela Tramonti Fiorenzo De Santis Eugenia Pennacchietti Daniela De Biase |
| author_sort | Angela Tramonti |
| collection | DOAJ |
| description | In order to survive the exposure to acid pH, <em>Escherichia coli</em> activates molecular circuits leading from acid tolerance to extreme acid resistance (AR). The activation of the different circuits involves several global and specific regulators affecting the expression of membrane, periplasmic and cytosolic proteins acting at different levels to dampen the harmful consequences of the uncontrolled entry of protons intracellularly. Many genes coding for the structural components of the <a></a><a>AR circuit</a>s (protecting from pH ≤ 2.5) and their specific transcriptional regulators cluster in a genomic region named AFI (acid fitness island) and respond in the same way to global regulators (such as RpoS and H-NS) as well as to anaerobiosis, alkaline, cold and respiratory stresses, in addition to the acid stress. Notably some genes coding for structural components of AR, though similarly regulated, are non-AFI localised. Amongst these the <em>gadBC</em> operon, coding for the major structural components of the glutamate-based AR system, and the <em>ybaS</em> gene, coding for a glutaminase required for the glutamine-based AR system. The <em>yhiM</em> gene, a non-AFI gene, appears to belong to this group. We mapped the transcription start of the 1.1 kb monocistronic <em>yhiM</em> transcript: it is an adenine residue located 22 nt upstream a GTG start codon. By real-time PCR we show that GadE and GadX equally affect the expression of <em>yhiM</em> under oxidative growth conditions. While YhiM is partially involved in the RpoS-dependent AR, we failed to detect a significant involvement in the glutamate- or glutamine-dependent AR at pH ≤ 2.5. However, when grown in EG at pH 5.0, the <em>yhiM</em> mutant displays impaired GABA export, whereas when YhiM is overexpressed, an increases of GABA export in EG medium in the pH range 2.5–5.5 is observed. Our data suggest that YhiM is a GABA transporter with a physiological role more relevant at mildly acidic pH, but not a key component of AR at pH < 2.5. |
| first_indexed | 2024-12-11T06:47:01Z |
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| institution | Directory Open Access Journal |
| issn | 2471-1888 |
| language | English |
| last_indexed | 2024-12-11T06:47:01Z |
| publishDate | 2017-02-01 |
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| spelling | doaj.art-2d9d1cdb03d54b4a84e27b41a19cd1bd2022-12-22T01:17:02ZengAIMS PressAIMS Microbiology2471-18882017-02-0131718710.3934/microbiol.2017.1.71microbiol-03-00071The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em>Angela Tramonti0Fiorenzo De Santis1Eugenia Pennacchietti2Daniela De Biase3Institute of Molecular Biology and Pathology, CNR, Department of Biochemical Sciences “A. Rossi Fanelli”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Roma, ItalyDepartment of medico-surgical Sciences and Biotechnologies, Sapienza University of Rome, Laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Corso della Repubblica 79, 04100 Latina, ItalyDepartment of medico-surgical Sciences and Biotechnologies, Sapienza University of Rome, Laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Corso della Repubblica 79, 04100 Latina, ItalyDepartment of medico-surgical Sciences and Biotechnologies, Sapienza University of Rome, Laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Corso della Repubblica 79, 04100 Latina, ItalyIn order to survive the exposure to acid pH, <em>Escherichia coli</em> activates molecular circuits leading from acid tolerance to extreme acid resistance (AR). The activation of the different circuits involves several global and specific regulators affecting the expression of membrane, periplasmic and cytosolic proteins acting at different levels to dampen the harmful consequences of the uncontrolled entry of protons intracellularly. Many genes coding for the structural components of the <a></a><a>AR circuit</a>s (protecting from pH ≤ 2.5) and their specific transcriptional regulators cluster in a genomic region named AFI (acid fitness island) and respond in the same way to global regulators (such as RpoS and H-NS) as well as to anaerobiosis, alkaline, cold and respiratory stresses, in addition to the acid stress. Notably some genes coding for structural components of AR, though similarly regulated, are non-AFI localised. Amongst these the <em>gadBC</em> operon, coding for the major structural components of the glutamate-based AR system, and the <em>ybaS</em> gene, coding for a glutaminase required for the glutamine-based AR system. The <em>yhiM</em> gene, a non-AFI gene, appears to belong to this group. We mapped the transcription start of the 1.1 kb monocistronic <em>yhiM</em> transcript: it is an adenine residue located 22 nt upstream a GTG start codon. By real-time PCR we show that GadE and GadX equally affect the expression of <em>yhiM</em> under oxidative growth conditions. While YhiM is partially involved in the RpoS-dependent AR, we failed to detect a significant involvement in the glutamate- or glutamine-dependent AR at pH ≤ 2.5. However, when grown in EG at pH 5.0, the <em>yhiM</em> mutant displays impaired GABA export, whereas when YhiM is overexpressed, an increases of GABA export in EG medium in the pH range 2.5–5.5 is observed. Our data suggest that YhiM is a GABA transporter with a physiological role more relevant at mildly acidic pH, but not a key component of AR at pH < 2.5.http://www.aimspress.com/microbiology/article/1267/fulltext.htmlinner membrane proteinsacid resistance<em>Escherichia coli</em>GadXGadEanaerobiosis |
| spellingShingle | Angela Tramonti Fiorenzo De Santis Eugenia Pennacchietti Daniela De Biase The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> AIMS Microbiology inner membrane proteins acid resistance <em>Escherichia coli</em> GadX GadE anaerobiosis |
| title | The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> |
| title_full | The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> |
| title_fullStr | The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> |
| title_full_unstemmed | The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> |
| title_short | The <em>yhiM</em> gene codes for an inner membrane protein involved in GABA export in <em>Escherichia coli</em> |
| title_sort | em yhim em gene codes for an inner membrane protein involved in gaba export in em escherichia coli em |
| topic | inner membrane proteins acid resistance <em>Escherichia coli</em> GadX GadE anaerobiosis |
| url | http://www.aimspress.com/microbiology/article/1267/fulltext.html |
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