Glutamine residues in Q-loops of multidrug resistance protein MRP1 contribute to ATP binding via interaction with metal cofactor.
Biochim Biophys Acta
; 1808(7): 1790-6, 2011 Jul.
Article
em En
| MEDLINE
| ID: mdl-21315686
ABSTRACT
Structural analyses of bacterial ATP-binding-cassette transporters revealed that the glutamine residue in Q-loop plays roles in interacting with 1) a metal cofactor to participate in ATP binding; 2) a putative catalytic water molecule to participate in ATP hydrolysis; 3) other residues to transmit the conformational changes between nucleotide-binding-domains and transmembrane-domains, in ATP-dependent solute transport. We have mutated the glutamines at 713 and 1375 to asparagine, methionine or leucine to determine the functional roles of these residues in Q-loops of MRP1. All these single mutants significantly decreased Mg·ATP binding and increased the K(m) (Mg·ATP) and V(max) values in Mg·ATP-dependent leukotriene-C4 transport. However, the V(max) values of the double mutants Q713N/Q1375N, Q713M/Q1375M and Q713L/Q1375L were lower than that of wtMRP1, implying that the double mutants cannot efficiently bind Mg·ATP. Interestingly, MRP1 has higher affinity for Mn·ATP than for Mg·ATP and the Mn·ATP-dependent leukotriene-C4 transport activities of Q713N/Q1375N and Q713M/Q1375M are significantly higher than that of wtMRP1. All these results suggest that 1) the glutamine residues in Q-loops contribute to ATP-binding via interaction with a metal cofactor; 2) it is most unlikely that these glutamine residues would play crucial roles in ATP hydrolysis and in transmitting the conformational changes between nucleotide-binding-domains and transmembrane-domains.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Trifosfato de Adenosina
/
Resistência a Múltiplos Medicamentos
/
Proteínas Associadas à Resistência a Múltiplos Medicamentos
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Glutamina
Limite:
Animals
/
Humans
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article