Ca(2+)-binding reduces conformational flexibility of RC-LH1 core complex from thermophile Thermochromatium tepidum.
Photosynth Res
; 111(1-2): 139-47, 2012 Mar.
Article
en En
| MEDLINE
| ID: mdl-22367594
ABSTRACT
The light-harvesting complex, LH1, of thermophile purple bacteria Thermochromatium tepidum consists of an array of α- and ß-polypeptides which assemble the photoactive bacteriochlorophyll and closely interact with the membrane-lipids. In this study, we investigated the effect of calcium and manganese ions on the protein structure and thermostability of the reaction centre (RC)-LH1/lipid complex. The binding of Ca(2+), but not Mn(2+) is shown to shift the LH1 Q ( y ) absorption maximum from ~889 to 915 nm and to significantly raise the thermostability of the RC-LH1 complex. The ATR-FTIR spectra indicate that interaction of Ca(2+) as monitored by the carboxylates' vibration of aspartate residues, but not Mn(2+) induces changes in the α-helix packing arrangement. The reduced rate of (1)H/(2)H exchange of proteins' amide protons shows that the accessibility to (2)H(2)O is significantly lowered in Ca(2+)-substituted RC-LH1/lipid complexes. In particular, exchange with the associated lipid molecules, is significantly retarded. These results suggest that the thermostability of the RC-LH1 complex is raised by the distinct interaction with calcium cations which reduces the RC-LH1/lipid dynamics, particularly, at the membrane-water interface.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Bacterioclorofilas
/
Calcio
/
Chromatiaceae
/
Proteínas del Complejo del Centro de Reacción Fotosintética
/
Complejos de Proteína Captadores de Luz
Idioma:
En
Revista:
Photosynth Res
Asunto de la revista:
METABOLISMO
Año:
2012
Tipo del documento:
Article
País de afiliación:
Alemania