@article{oai:rose-ibadai.repo.nii.ac.jp:00010250,
 author = {KIMURA, Yukihiro / YU, Long Jiang / HIRANO, Yu / SUZUKI, Hiroaki / WANG, Zheng Yu},
 issue = {284},
 journal = {The Journal of Biological Chemistry},
 month = {Jan},
 note = {application/pdf, 論文(Article), Thermochromatium (Tch.) tepidum is a
thermophilic purple sulfur photosynthetic
bacterium collected from the Mammoth Hot
Springs, Yellowstone National Park. A
previous study showed that the lightharvesting-
reaction center core complex (LH1-
RC) purified from this bacterium is highly
stable at room temperature [Suzuki et al.,
(2007) Biochim. Biophys. Acta 1767, 1057-1063].
In this work, we demonstrate that thermal
stability of the Tch. tepidum LH1-RC is much
higher than that of its mesophilic counterparts
and the enhanced thermal stability requires
Ca2+ as a cofactor. Removal of the Ca2+ from
Tch. tepidum LH1-RC resulted in a complex
with the same degree of thermal stability to
that of the LH1-RCs purified from mesophilic
bacteria. The enhanced thermal stability can
be restored by addition of Ca2+ to the Ca2+-
depleted LH1-RC, and this process is fully
reversible. Interchange of the thermal
stability between the two forms is accompanied
by a shift of the LH1 Qy transition between 915
nm for the native and 880 nm for the Ca2+-
depleted LH1-RC. Differential scanning
calorimetry measurements reveal that
degradation temperature of the native LH1-RC
is 15 °C higher and the enthalpy change is
about 28% larger than the Ca2+-depleted LH1-
RC. Substitution of the Ca2+ with other metal
cations caused a decrease in thermal stability of
extent depending on the properties of the
cations. These results indicate that Ca2+ ions
play a dual role in stabilizing the structure of
the pigment-membrane protein complex and
altering its spectroscopic properties, and hence
provide insight into the adaptive strategy of
this photosynthetic organism to survive in
extreme environments using natural resources.},
 pages = {93--99},
 title = {Calcium ions are required for the enhanced thermal stability of the light-harvesting-reaction center core complex from thermophilic purple sulfur bacterium Thermochromatium tepidum},
 year = {2009}
}