A conserved leucine occupies the empty substrate site of LeuT in the Na(+)-free return state.
Nat Commun
; 7: 11673, 2016 05 25.
Article
em En
| MEDLINE
| ID: mdl-27221344
ABSTRACT
Bacterial members of the neurotransmittersodium symporter (NSS) family perform Na(+)-dependent amino-acid uptake and extrude H(+) in return. Previous NSS structures represent intermediates of Na(+)/substrate binding or intracellular release, but not the inward-to-outward return transition. Here we report crystal structures of Aquifex aeolicus LeuT in an outward-oriented, Na(+)- and substrate-free state likely to be H(+)-occluded. We find a remarkable rotation of the conserved Leu25 into the empty substrate-binding pocket and rearrangements of the empty Na(+) sites. Mutational studies of the equivalent Leu99 in the human serotonin transporter show a critical role of this residue on the transport rate. Molecular dynamics simulations show that extracellular Na(+) is blocked unless Leu25 is rotated out of the substrate-binding pocket. We propose that Leu25 facilitates the inward-to-outward transition by compensating a Na(+)- and substrate-free state and acts as the gatekeeper for Na(+) binding that prevents leak in inward-outward return transitions.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Sistemas de Transporte de Aminoácidos
/
Proteínas da Membrana Plasmática de Transporte de Neurotransmissores
Limite:
Humans
Idioma:
En
Revista:
Nat Commun
Assunto da revista:
BIOLOGIA
/
CIENCIA
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Dinamarca