Abstract
The light-harvesting 1 reaction center (LH1-RC) complex from thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits enhanced thermostability and an unusual LH1 Qy transition, both induced by Ca2+ binding. In this study, metal-binding sites and metal-protein interactions in the LH1-RC complexes from wild-type (B915) and biosynthetically Sr2+-substituted (B888) Tch. tepidum were investigated by isothermal titration calorimetry (ITC), atomic absorption (AA), and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopies. The ITC measurements revealed stoichiometric ratios of approximately 1:1 for binding of Ca2+, Sr2+, or Ba2+ to the LH1 αβ-subunit, indicating the presence of 16 binding sites in both B915 and B888. The AA analysis provided direct evidence for Ca2+ and Sr2+ binding to B915 and B888, respectively, in their purified states. Metal-binding experiments supported that Ca2+ and Sr2+ (or Ba2+) competitively associate with the binding sites in both species. The ATR-FTIR difference spectra upon Ca2+ depletion and Sr2+ substitution demonstrated that dissociation and binding of Ca2+ are predominantly responsible for metal-dependent conformational changes of B915 and B888. The present results are largely compatible with the recent structural evidence that another binding site for Sr2+ (or Ba2+) exists in the vicinity of the Ca2+-binding site, a part of which is shared in both metal-binding sites. (Graph Presented).
| Original language | English |
|---|---|
| Pages (from-to) | 12466-12473 |
| Number of pages | 8 |
| Journal | Journal of Physical Chemistry B |
| Volume | 120 |
| Issue number | 49 |
| DOIs | |
| Publication status | Published - Dec 15 2016 |
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ASJC Scopus subject areas
- Surfaces, Coatings and Films
- Physical and Theoretical Chemistry
- Materials Chemistry
Cite this
Spectroscopic and Thermodynamic Characterization of the Metal-Binding Sites in the LH1-RC Complex from Thermophilic Photosynthetic Bacterium Thermochromatium tepidum. / Kimura, Yukihiro; Yura, Yuki; Hayashi, Yusuke; Li, Yong; Onoda, Moe; Yu, Long-Jiang; Wang-Otomo, Zheng Yu; Ohno, Takashi.
In: Journal of Physical Chemistry B, Vol. 120, No. 49, 15.12.2016, p. 12466-12473.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Spectroscopic and Thermodynamic Characterization of the Metal-Binding Sites in the LH1-RC Complex from Thermophilic Photosynthetic Bacterium Thermochromatium tepidum
AU - Kimura, Yukihiro
AU - Yura, Yuki
AU - Hayashi, Yusuke
AU - Li, Yong
AU - Onoda, Moe
AU - Yu, Long-Jiang
AU - Wang-Otomo, Zheng Yu
AU - Ohno, Takashi
PY - 2016/12/15
Y1 - 2016/12/15
N2 - The light-harvesting 1 reaction center (LH1-RC) complex from thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits enhanced thermostability and an unusual LH1 Qy transition, both induced by Ca2+ binding. In this study, metal-binding sites and metal-protein interactions in the LH1-RC complexes from wild-type (B915) and biosynthetically Sr2+-substituted (B888) Tch. tepidum were investigated by isothermal titration calorimetry (ITC), atomic absorption (AA), and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopies. The ITC measurements revealed stoichiometric ratios of approximately 1:1 for binding of Ca2+, Sr2+, or Ba2+ to the LH1 αβ-subunit, indicating the presence of 16 binding sites in both B915 and B888. The AA analysis provided direct evidence for Ca2+ and Sr2+ binding to B915 and B888, respectively, in their purified states. Metal-binding experiments supported that Ca2+ and Sr2+ (or Ba2+) competitively associate with the binding sites in both species. The ATR-FTIR difference spectra upon Ca2+ depletion and Sr2+ substitution demonstrated that dissociation and binding of Ca2+ are predominantly responsible for metal-dependent conformational changes of B915 and B888. The present results are largely compatible with the recent structural evidence that another binding site for Sr2+ (or Ba2+) exists in the vicinity of the Ca2+-binding site, a part of which is shared in both metal-binding sites. (Graph Presented).
AB - The light-harvesting 1 reaction center (LH1-RC) complex from thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits enhanced thermostability and an unusual LH1 Qy transition, both induced by Ca2+ binding. In this study, metal-binding sites and metal-protein interactions in the LH1-RC complexes from wild-type (B915) and biosynthetically Sr2+-substituted (B888) Tch. tepidum were investigated by isothermal titration calorimetry (ITC), atomic absorption (AA), and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopies. The ITC measurements revealed stoichiometric ratios of approximately 1:1 for binding of Ca2+, Sr2+, or Ba2+ to the LH1 αβ-subunit, indicating the presence of 16 binding sites in both B915 and B888. The AA analysis provided direct evidence for Ca2+ and Sr2+ binding to B915 and B888, respectively, in their purified states. Metal-binding experiments supported that Ca2+ and Sr2+ (or Ba2+) competitively associate with the binding sites in both species. The ATR-FTIR difference spectra upon Ca2+ depletion and Sr2+ substitution demonstrated that dissociation and binding of Ca2+ are predominantly responsible for metal-dependent conformational changes of B915 and B888. The present results are largely compatible with the recent structural evidence that another binding site for Sr2+ (or Ba2+) exists in the vicinity of the Ca2+-binding site, a part of which is shared in both metal-binding sites. (Graph Presented).
UR - http://www.scopus.com/inward/record.url?scp=85006270278&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85006270278&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.6b10068
DO - 10.1021/acs.jpcb.6b10068
M3 - Article
C2 - 27973820
AN - SCOPUS:85006270278
VL - 120
SP - 12466
EP - 12473
JO - Journal of Physical Chemistry B Materials
JF - Journal of Physical Chemistry B Materials
SN - 1520-6106
IS - 49
ER -