SERCA mutant E309Q binds two Ca(2+) ions but adopts a catalytically incompetent conformation.
EMBO J
; 32(24): 3231-43, 2013 Dec 11.
Article
en En
| MEDLINE
| ID: mdl-24270570
ABSTRACT
The sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) couples ATP hydrolysis to transport of Ca(2+). This directed energy transfer requires cross-talk between the two Ca(2+) sites and the phosphorylation site over 50 Å distance. We have addressed the mechano-structural basis for this intramolecular signal by analysing the structure and the functional properties of SERCA mutant E309Q. Glu(309) contributes to Ca(2+) coordination at site II, and a consensus has been that E309Q only binds Ca(2+) at site I. The crystal structure of E309Q in the presence of Ca(2+) and an ATP analogue, however, reveals two occupied Ca(2+) sites of a non-catalytic Ca2E1 state. Ca(2+) is bound with micromolar affinity by both Ca(2+) sites in E309Q, but without cooperativity. The Ca(2+)-bound mutant does phosphorylate from ATP, but at a very low maximal rate. Phosphorylation depends on the correct positioning of the A-domain, requiring a shift of transmembrane segment M1 into an 'up and kinked position'. This transition is impaired in the E309Q mutant, most likely due to a lack of charge neutralization and altered hydrogen binding capacities at Ca(2+) site II.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Calcio
/
ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
EMBO J
Año:
2013
Tipo del documento:
Article
País de afiliación:
Dinamarca