Critical roles of the CuB site in efficient proton pumping as revealed by crystal structures of mammalian cytochrome c oxidase catalytic intermediates.
J Biol Chem
; 297(3): 100967, 2021 09.
Article
en En
| MEDLINE
| ID: mdl-34274318
Mammalian cytochrome c oxidase (CcO) reduces O2 to water in a bimetallic site including Fea3 and CuB giving intermediate molecules, termed A-, P-, F-, O-, E-, and R-forms. From the P-form on, each reaction step is driven by single-electron donations from cytochrome c coupled with the pumping of a single proton through the H-pathway, a proton-conducting pathway composed of a hydrogen-bond network and a water channel. The proton-gradient formed is utilized for ATP production by F-ATPase. For elucidation of the proton pumping mechanism, crystal structural determination of these intermediate forms is necessary. Here we report X-ray crystallographic analysis at â¼1.8 Å resolution of fully reduced CcO crystals treated with O2 for three different time periods. Our disentanglement of intermediate forms from crystals that were composed of multiple forms determined that these three crystallographic data sets contained â¼45% of the O-form structure, â¼45% of the E-form structure, and â¼20% of an oxymyoglobin-type structure consistent with the A-form, respectively. The O- and E-forms exhibit an unusually long CuB2+-OH- distance and CuB1+-H2O structure keeping Fea33+-OH- state, respectively, suggesting that the O- and E-forms have high electron affinities that cause the OâE and EâR transitions to be essentially irreversible and thus enable tightly coupled proton pumping. The water channel of the H-pathway is closed in the O- and E-forms and partially open in the R-form. These structures, together with those of the recently reported P- and F-forms, indicate that closure of the H-pathway water channel avoids back-leaking of protons for facilitating the effective proton pumping.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Bombas de Protones
/
Complejo IV de Transporte de Electrones
/
Cobre
/
Mitocondrias Cardíacas
Límite:
Animals
Idioma:
En
Revista:
J Biol Chem
Año:
2021
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Estados Unidos