Szilágyi A, Závodszky P
Department of Biological Physics, Institute of Enzymology, Biological Research Centre, Hungarian Academy of Sciences, Eötvös Loránd University, Budapest, H-1518 Pf. 7, H-1117, Hungary.
Structure. 2000 May 15;8(5):493-504. doi: 10.1016/s0969-2126(00)00133-7.
Proteins from thermophilic organisms usually show high intrinsic thermal stability but have structures that are very similar to their mesophilic homologues. From prevous studies it is difficult to draw general conclusions about the structural features underlying the increased thermal stability of thermophilic proteins.
In order to reveal the general evolutionary strategy for changing the heat stability of proteins, a non-redundant data set was compiled comprising all high-quality structures of thermophilic proteins and their mesophilic homologues from the Protein Data Bank. The selection (quality) criteria were met by 64 mesophilic and 29 thermophilic protein subunits, representing 25 protein families. From the atomic coordinates, 13 structural parameters were calculated, compared and evaluated using statistical methods. This study is distinguished from earlier ones by the strict quality control of the structures used and the size of the data set.
Different protein families adapt to higher temperatures by different sets of structural devices. Regarding the structural parameters, the only generally observed rule is an increase in the number of ion pairs with increasing growth temperature. Other parameters show just a trend, whereas the number of hydrogen bonds and the polarity of buried surfaces exhibit no clear-cut tendency to change with growth temperature. Proteins from extreme thermophiles are stabilized in different ways to moderately thermophilic ones. The preferences of these two groups are different with regards to the number of ion pairs, the number of cavities, the polarity of exposed surface and the secondary structural composition.
嗜热生物的蛋白质通常具有较高的内在热稳定性，但其结构与其嗜温同源物非常相似。从先前的研究中，很难就嗜热蛋白质热稳定性增加背后的结构特征得出一般性结论。
为了揭示改变蛋白质热稳定性的一般进化策略，编制了一个非冗余数据集，该数据集包含来自蛋白质数据库的嗜热蛋白质及其嗜温同源物的所有高质量结构。64个嗜温蛋白亚基和29个嗜热蛋白亚基满足选择（质量）标准，代表25个蛋白质家族。从原子坐标计算了13个结构参数，并使用统计方法进行比较和评估。本研究与早期研究的不同之处在于对所用结构的严格质量控制和数据集的大小。
不同的蛋白质家族通过不同的结构装置组合来适应更高的温度。关于结构参数，唯一普遍观察到的规律是随着生长温度的升高离子对数量增加。其他参数仅显示出一种趋势，而氢键数量和埋藏表面的极性在生长温度变化时没有明显的变化趋势。极端嗜热菌的蛋白质与中度嗜热菌的蛋白质以不同方式稳定。这两组在离子对数量、空穴数量、暴露表面的极性和二级结构组成方面的偏好不同。
