Conformational transitions of membrane-spanning peptides

包埋在细胞膜中的蛋白质占人类基因组的三分之一。它们调节穿过生物膜的分子交通和信息流，并且因此代表用于活细胞中的过程的研究和/或调节的有吸引力的生物分子。 据估计，目前所有药物靶标中约70%是膜蛋白。 然而，膜蛋白目前占蛋白质数据库中存放的>56000种结构的1-2%，部分原因是与这些高度疏水分子的纯化和结构表征相关的技术挑战。幸运的是，深入了解膜蛋白折叠并不完全依赖于高分辨率结构的可用性，而是通过生产单个跨膜（TM）序列作为合成肽来促进。这些肽模型的优点在于它们能够复制天然螺旋-螺旋接触，以足够的量产生用于结构分析，以及它们能够通过各种生物物理技术进行研究。 我们在这里提出了一系列的实验，这些原则被实施调查的结构和序列的决定因素TM段识别的细胞机器，以评估如何跨膜肽的侧链化学有助于膜插入和折叠，并使用跨膜肽与His残基标记筛选膜蛋白的合作伙伴。与肽序列的明智设计和适当的膜模拟介质的选择相一致，在这些肽中观察到的螺旋-螺旋相互作用可以被预期为非常接近其天然结构中的TM结构域相互作用。结果将有助于定义膜蛋白折叠中结构-功能关系的关键原则，并在更长的范围内，提供有关这些因素如何在疾病状态下变得异常的见解。

Proteins embedded in membranes comprise fully one-third of the human genome. They regulate the molecular traffic and information flow across biological membranes and, as such, represent attractive biomolecules for the study and/or modulation of processes in living cells. It is estimated that approximately 70% of all current pharmaceutical targets are membrane proteins. Yet membrane proteins currently represent 1-2% of the >56000 structures deposited in the Protein Data Bank, in part because of the technical challenges associated with the purification, and structural characterization of these highly hydrophobic molecules. Fortunately, gaining insight into membrane protein folding has not relied exclusively on the availability of high-resolution structures, but has been facilitated by the production of individual transmembrane (TM) sequences as synthetic peptides. The advantages of these peptide models lie in their ability to replicate native helix-helix contacts, to be produced in sufficient quantities for structural analysis, and in their amenability to studies by a variety of biophysical techniques. We propose here a series of experiments where these principles are implemented to investigate structure and sequence determinants of TM segment recognition by cellular machinery; to evaluate how the side chain chemistry of membrane-spanning peptides contributes to membrane insertion and folding; and to use membrane spanning peptides tagged with His residues to screen for membrane protein partners. In concert with the judicious design of peptide sequences and choice of appropriate membrane-mimetic media, the helix-helix interactions observed in these peptides may be expected to closely approximate the TM domain interactions in their native structures. Results will help define key principles about structure-function relationships in membrane protein folding, and in the longer range, provide insights as to how these factors become aberrant in disease states.