Insights into the molecular basis for substrate binding and specificity of the wild-type L-arginine/agmatine antiporter AdiC.
Proc Natl Acad Sci U S A
; 113(37): 10358-63, 2016 09 13.
Article
em En
| MEDLINE
| ID: mdl-27582465
ABSTRACT
Pathogenic enterobacteria need to survive the extreme acidity of the stomach to successfully colonize the human gut. Enteric bacteria circumvent the gastric acid barrier by activating extreme acid-resistance responses, such as the arginine-dependent acid resistance system. In this response, l-arginine is decarboxylated to agmatine, thereby consuming one proton from the cytoplasm. In Escherichia coli, the l-arginine/agmatine antiporter AdiC facilitates the export of agmatine in exchange of l-arginine, thus providing substrates for further removal of protons from the cytoplasm and balancing the intracellular pH. We have solved the crystal structures of wild-type AdiC in the presence and absence of the substrate agmatine at 2.6-Å and 2.2-Å resolution, respectively. The high-resolution structures made possible the identification of crucial water molecules in the substrate-binding sites, unveiling their functional roles for agmatine release and structure stabilization, which was further corroborated by molecular dynamics simulations. Structural analysis combined with site-directed mutagenesis and the scintillation proximity radioligand binding assay improved our understanding of substrate binding and specificity of the wild-type l-arginine/agmatine antiporter AdiC. Finally, we present a potential mechanism for conformational changes of the AdiC transport cycle involved in the release of agmatine into the periplasmic space of E. coli.
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1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Antiporters
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Proteínas de Escherichia coli
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Sistemas de Transporte de Aminoácidos
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2016
Tipo de documento:
Article