A new type of Na(+)-driven ATP synthase membrane rotor with a two-carboxylate ion-coupling motif.
PLoS Biol
; 11(6): e1001596, 2013.
Article
em En
| MEDLINE
| ID: mdl-23824040
ABSTRACT
The anaerobic bacterium Fusobacterium nucleatum uses glutamate decarboxylation to generate a transmembrane gradient of Naâº. Here, we demonstrate that this ion-motive force is directly coupled to ATP synthesis, via an F1F0-ATP synthase with a novel Na⺠recognition motif, shared by other human pathogens. Molecular modeling and free-energy simulations of the rotary element of the enzyme, the c-ring, indicate Na⺠specificity in physiological settings. Consistently, activity measurements showed Na⺠stimulation of the enzyme, either membrane-embedded or isolated, and ATP synthesis was sensitive to the Na⺠ionophore monensin. Furthermore, Na⺠has a protective effect against inhibitors targeting the ion-binding sites, both in the complete ATP synthase and the isolated c-ring. Definitive evidence of Na⺠coupling is provided by two identical crystal structures of the c11 ring, solved by X-ray crystallography at 2.2 and 2.6 Å resolution, at pH 5.3 and 8.7, respectively. Na⺠ions occupy all binding sites, each coordinated by four amino acids and a water molecule. Intriguingly, two carboxylates instead of one mediate ion binding. Simulations and experiments demonstrate that this motif implies that a proton is concurrently bound to all sites, although Na⺠alone drives the rotary mechanism. The structure thus reveals a new mode of ion coupling in ATP synthases and provides a basis for drug-design efforts against this opportunistic pathogen.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Sódio
/
Membrana Celular
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Fusobacterium nucleatum
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ATPases Mitocondriais Próton-Translocadoras
Limite:
Humans
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article