Bywater Robert P
Computational Biology Laboratory, Francis Crick Institute, London NW1 1AT, England, UK.
Heliyon. 2017 May 30;3(5):e00307. doi: 10.1016/j.heliyon.2017.e00307. eCollection 2017 May.
Hydrogen-bonding networks in proteins considered as structural tensile elements are in balance separately from any other stabilising interactions that may be in operation. The hydrogen bond arrangement in the network is reminiscent of tensegrity structures in architecture and sculpture. Tensegrity has been discussed before in cells and tissues and in proteins. In contrast to previous work only hydrogen bonds are studied here. The other interactions within proteins are either much stronger - covalent bonds connecting the atoms in the molecular skeleton or weaker forces like the so-called hydrophobic interactions. It has been demonstrated that the latter operate independently from hydrogen bonds. Each category of interaction must, if the protein is to have a stable structure, balance out. The hypothesis here is that the entire hydrogen bond network is in balance without any compensating contributions from other types of interaction. For sidechain-sidechain, sidechain-backbone and backbone-backbone hydrogen bonds in proteins, tensegrity balance ("closure") is required over the entire length of the polypeptide chain that defines individually folding units in globular proteins ("domains") as well as within the repeating elements in fibrous proteins that consist of extended chain structures. There is no closure to be found in extended structures that do not have repeating elements. This suggests an explanation as to why globular domains, as well as the repeat units in fibrous proteins, have to have a defined number of residues. Apart from networks of sidechain-sidechain hydrogen bonds there are certain key points at which this closure is achieved in the sidechain-backbone hydrogen bonds and these are associated with demarcation points at the start or end of stretches of secondary structure. Together, these three categories of hydrogen bond achieve the closure that is necessary for the stability of globular protein domains as well as repeating elements in fibrous proteins.
被视为结构拉伸元件的蛋白质中的氢键网络，与可能正在起作用的任何其他稳定相互作用是分开平衡的。网络中的氢键排列让人联想到建筑和雕塑中的张拉整体结构。之前已经在细胞、组织和蛋白质中讨论过张拉整体结构。与之前的工作不同，这里只研究氢键。蛋白质中的其他相互作用要么强得多——连接分子骨架中原子的共价键，要么弱得多——比如所谓的疏水相互作用。已经证明，后者独立于氢键起作用。如果蛋白质要有稳定的结构，每一类相互作用都必须达到平衡。这里的假设是，整个氢键网络处于平衡状态，没有来自其他类型相互作用的任何补偿贡献。对于蛋白质中的侧链 - 侧链、侧链 - 主链和主链 - 主链氢键，在定义球状蛋白质（“结构域”）中单独折叠单元的多肽链的整个长度上，以及在由延伸链结构组成的纤维状蛋白质的重复元件内，都需要张拉整体平衡（“封闭”）。在没有重复元件的延伸结构中找不到封闭。这就解释了为什么球状结构域以及纤维状蛋白质中的重复单元必须有确定数量的残基。除了侧链 - 侧链氢键网络外，在侧链 - 主链氢键中还有某些关键点实现了这种封闭，这些点与二级结构片段起始或末端的分界点相关。这三类氢键共同实现了球状蛋白质结构域以及纤维状蛋白质中重复元件稳定性所必需的封闭。
