Privalov Peter L, Crane-Robinson Colyn
Department of Biology, Johns Hopkins University, Baltimore, MD, 21218, USA.
Biophysics Laboratories, School of Biology, University of Portsmouth, Portsmouth, PO1 2DT, UK.
Eur Biophys J. 2017 Apr;46(3):203-224. doi: 10.1007/s00249-016-1161-y. Epub 2016 Jul 25.
This review shows that water in biological systems is not just a passive liquid solvent but also a partner in the formation of the structure of proteins, nucleic acids and their complexes, thereby contributing to the stability and flexibility required for their proper function. Reciprocally, biological macromolecules affect the state of the water contacting them, so that it is only partly in the normal liquid state, being somewhat ordered when bound to macromolecules. While the compaction of globular proteins results from the reluctance of their hydrophobic groups to interact with water, the collagen superhelix is maintained by water forming a hydroxyproline-controlled frame around this coiled-coil macromolecule. As for DNA, its stability and rigidity are linked to water fixed by AT pairs in the minor groove: this leads to the enthalpic contribution of AT pairs exceeding that of GC pairs, but this is overbalanced by their greater entropy contribution, with the result that AT pairs melt at lower temperatures than GCs. Loss of this water drives transcription factor binding to the minor groove.
这篇综述表明，生物系统中的水不仅是一种被动的液体溶剂，也是蛋白质、核酸及其复合物结构形成过程中的参与者，从而有助于其正常功能所需的稳定性和灵活性。相反，生物大分子会影响与其接触的水的状态，因此水只有部分处于正常液态，在与大分子结合时会有一定程度的有序排列。球状蛋白质的紧密结构是由于其疏水基团不愿与水相互作用导致的，而胶原蛋白超螺旋则通过水在这种卷曲螺旋大分子周围形成一个由羟脯氨酸控制的框架来维持。至于DNA，其稳定性和刚性与小沟中由AT碱基对固定的水有关：这导致AT碱基对的焓贡献超过GC碱基对，但由于它们更大的熵贡献，这种情况被抵消，结果是AT碱基对比GC碱基对在更低温度下解链。这种水的丢失会促使转录因子与小沟结合。
