Robinson-Rechavi Marc, Alibés Andreu, Godzik Adam
Joint Center for Structural Genomics, University of California, San Diego, La Jolla, 92093-0527, USA.
J Mol Biol. 2006 Feb 17;356(2):547-57. doi: 10.1016/j.jmb.2005.11.065. Epub 2005 Dec 7.
Studies of the structural basis of protein thermostability have produced a confusing picture. Small sets of proteins have been analyzed from a variety of thermophilic species, suggesting different structural features as responsible for protein thermostability. Taking advantage of the recent advances in structural genomics, we have compiled a relatively large protein structure dataset, which was constructed very carefully and selectively; that is, the dataset contains only experimentally determined structures of proteins from one specific organism, the hyperthermophilic bacterium Thermotoga maritima, and those of close homologs from mesophilic bacteria. In contrast to the conclusions of previous studies, our analyses show that oligomerization order, hydrogen bonds, and secondary structure play minor roles in adaptation to hyperthermophily in bacteria. On the other hand, the data exhibit very significant increases in the density of salt-bridges and in compactness for proteins from T.maritima. The latter effect can be measured by contact order or solvent accessibility, and network analysis shows a specific increase in highly connected residues in this thermophile. These features account for changes in 96% of the protein pairs studied. Our results provide a clear picture of protein thermostability in one species, and a framework for future studies of thermal adaptation.
对蛋白质热稳定性结构基础的研究结果令人困惑。人们已经对来自多种嗜热物种的少量蛋白质进行了分析，结果表明不同的结构特征是蛋白质热稳定性的原因。利用结构基因组学的最新进展，我们编制了一个相对较大的蛋白质结构数据集，该数据集构建得非常仔细且具有选择性；也就是说，该数据集仅包含来自一种特定生物体——嗜热细菌海栖热袍菌（Thermotoga maritima）的蛋白质以及来自嗜温细菌的近缘同源物的实验确定结构。与先前研究的结论相反，我们的分析表明，寡聚化顺序、氢键和二级结构在细菌适应嗜热环境中起次要作用。另一方面，数据显示海栖热袍菌蛋白质的盐桥密度和紧凑性显著增加。后者的效应可以通过接触顺序或溶剂可及性来衡量，网络分析表明这种嗜热菌中高度连接的残基有特定增加。这些特征解释了所研究的96%的蛋白质对的变化。我们的结果清晰地呈现了一个物种中蛋白质的热稳定性情况，并为未来的热适应研究提供了一个框架。
