Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides.
Biochemistry
; 54(12): 2104-16, 2015 Mar 31.
Article
em En
| MEDLINE
| ID: mdl-25734689
ABSTRACT
Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, we have investigated and characterized the interactions of the protein with the quinones in the Q(A) and Q(B) sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Q(B) site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the Q(A) and Q(B) sites. Disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the Q(A)â»Q(B)â» biradical and competitive binding assays.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Rhodobacter sphaeroides
/
Complexo de Proteínas do Centro de Reação Fotossintética
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos