Conserved Asp684 in transmembrane segment M6 of the plant plasma membrane P-type proton pump AHA2 is a molecular determinant of proton translocation.
J Biol Chem
; 278(20): 17845-51, 2003 May 16.
Article
em En
| MEDLINE
| ID: mdl-12626496
ABSTRACT
The mechanism of proton pumping by P-type H(+)-ATPases is still unclear. In the plant P-type plasma membrane H(+)-ATPase AHA2, two charged residues, Arg(655) and Asp(684), are conserved in transmembrane segments M5 and M6, respectively, a region that has been shown be contribute to ion coordination in related P-type ATPases. Substitution of Arg(655) with either alanine or aspartate resulted in mutant enzymes exhibiting a significant shift in the P-type ATPase E(1)P-E(2)P conformational equilibrium. The mutant proteins accumulated in the E(1)P conformation, but were capable of conducting proton transport. This points to an important role of Arg(655) in the E(1)P-E(2)P conformational transition. The presence of a carboxylate moiety at position Asp(684) proved essential for coupling between initial proton binding and proton pumping. The finding that the carboxylate side chain of Asp(684) contributes to the proton-binding site and appears to function as an absolutely essential proton acceptor along the proton transport pathway is discussed in the context of a possible proton pumping mechanism of P-type H(+)-ATPases.
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Base de dados:
MEDLINE
Assunto principal:
Membrana Celular
/
Ácido Aspártico
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article