Masanari Misa, Fujii Sotaro, Kawahara Kazuki, Oki Hiroya, Tsujino Hirofumi, Maruno Takahiro, Kobayashi Yuji, Ohkubo Tadayasu, Wakai Satoshi, Sambongi Yoshihiro
a Graduate School of Biosphere Science , Hiroshima University , Higashi-Hiroshima , Japan.
b Graduate School of Pharmaceutical Sciences , Osaka University , Suita , Japan.
Biosci Biotechnol Biochem. 2016 Dec;80(12):2365-2370. doi: 10.1080/09168451.2016.1232155. Epub 2016 Sep 20.
Monomeric cytochrome c from deep-sea piezophilic Shewanella violacea (SVcytc) was stable against heat and denaturant compared with the homologous protein from shallow-sea piezo-sensitive Shewanella livingstonensis (SLcytc). Here, the SVcytc crystal structure revealed that the Lys-50 side chain on the flexible loop formed a hydrogen bond with heme whereas that of corresponding hydrophobic Leu-50 could not form such a bond in SLcytc, which appeared to be one of possible factors responsible for the difference in stability between the two proteins. This structural insight was confirmed by a reciprocal mutagenesis study on the thermal stability of these two proteins. As SVcytc was isolated from a deep-sea piezophilic bacterium, the present comparative study indicates that adaptation of monomeric SVcytc to high pressure environments results in stabilization against heat.
与来自浅海压敏希瓦氏菌（SLcytc）的同源蛋白相比，深海嗜压希瓦氏菌（SVcytc）的单体细胞色素c对热和变性剂具有更高的稳定性。在此，SVcytc的晶体结构显示，柔性环上的赖氨酸-50侧链与血红素形成了氢键，而在SLcytc中相应的疏水亮氨酸-50则无法形成这种键，这似乎是导致这两种蛋白质稳定性差异的可能因素之一。通过对这两种蛋白质热稳定性的相互诱变研究证实了这一结构见解。由于SVcytc是从深海嗜压细菌中分离出来的，目前的比较研究表明，单体SVcytc对高压环境的适应性导致了其对热的稳定性。
