嗜热栖热放线菌中细胞色素c550的氧化还原电位。
Redox potential of cytochrome c550 in the cyanobacterium Thermosynechococcus elongates.
作者信息
Ishikita Hiroshi, Knapp Ernst-Walter
机构信息
Institute of Chemistry, Department of Biology, Chemistry, and Pharmacy, Free University of Berlin, Takustrasse 6, D-14195 Berlin, Germany.
出版信息
FEBS Lett. 2005 Jun 6;579(14):3190-4. doi: 10.1016/j.febslet.2005.05.004.
Cytochrome c550 (cyt c550) from photosystem II (PSII) exists in the PSII-bound form but can be released from PSII by treatment with divalent cations or Tris, yielding the isolated form. We calculated heme redox potentials (Em) based on the crystal structures of cyt c550 by solving the Poisson-Boltzmann equation. In the isolated form, the calculated Em are -240 mV at pH 6.0 and -352 mV at pH 9.0. This pH-dependence is predominantly due to deprotonation of the heme-propionic group near Asn-49. In the PSII-bound form, the calculated E(m) was up-shifted by 160 mV versus the isolated form due to a conformational change of protein backbone, yielding Em=-84 mV.
来自光系统II（PSII）的细胞色素c550（cyt c550）以与PSII结合的形式存在，但通过用二价阳离子或Tris处理可从PSII中释放出来，从而得到分离形式。我们通过求解泊松-玻尔兹曼方程，根据cyt c550的晶体结构计算了血红素氧化还原电位（Em）。在分离形式下，在pH 6.0时计算得到的Em为-240 mV，在pH 9.0时为-352 mV。这种pH依赖性主要是由于靠近Asn-49的血红素-丙酸基团的去质子化。在与PSII结合的形式中，由于蛋白质主链的构象变化，计算得到的E(m)相对于分离形式上移了160 mV，得到Em = -84 mV。
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