Aqueous access channels in subunit a of rotary ATP synthase.
J Biol Chem
; 278(8): 6066-74, 2003 Feb 21.
Article
em En
| MEDLINE
| ID: mdl-12473663
ABSTRACT
The role of subunit a in proton translocation by the Escherichia coli F(1)F(o) ATP synthase is poorly understood. In the membrane-bound F(o) sector of the enzyme, H(+) binding and release occurs at Asp(61) in the middle of the second transmembrane helix (TMH) of subunit c. Protons are thought to reach Asp(61) via an aqueous access pathway formed at least in part by one or more of the five TMHs of subunit a. In this report, we have substituted Cys into a 19-residue span of the fourth TMH of subunit a and used chemical modification to obtain information about the aqueous accessibility of residues along this helix. Residues 206, 210, and 214 are N-ethylmaleimide-accessible from the cytoplasmic side of the membrane and may lie on the H(+) transport route. Residues 215 and 218 on TMH4, as well as residue 245 on TMH5, are Ag(+)-accessible but N-ethylmaleimide-inaccessible and may form part of an aqueous pocket extending from Asp(61) of subunit c to the periplasmic surface.
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Base de dados:
MEDLINE
Assunto principal:
Trifosfato de Adenosina
/
ATPases Mitocondriais Próton-Translocadoras
/
Escherichia coli
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article