Conformational transitions of membrane-spanning peptides

嵌入在膜中的蛋白质完全构成了人类基因组的三分之一。它们调节通过生物膜的分子交通和信息流，因此，它们是研究和/或调节活细胞过程的有吸引力的生物分子。据估计，目前所有药物靶标中约有70%是膜蛋白。然而，膜蛋白目前占蛋白质数据库中储存的&gt；56000结构的1-2%，部分原因是与这些高度疏水的分子的纯化和结构表征相关的技术挑战。幸运的是，对膜蛋白折叠的深入了解并不完全依赖于高分辨率结构的可用性，而是通过生产作为合成肽的单个跨膜(TM)序列来促进。这些多肽模型的优势在于它们能够复制天然的螺旋-螺旋接触，能够产生足够的数量用于结构分析，并且它们适合于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实验，在这些实验中，我们将应用这些原理来研究细胞机械识别TM片段的结构和序列决定因素；评估跨膜多肽的侧链化学如何促进膜插入和折叠；以及使用标记有His残基的跨膜多肽来筛选膜蛋白伙伴。结合正确的多肽序列设计和合适的膜模拟介质的选择，这些多肽中观察到的螺旋-螺旋相互作用可能与它们天然结构中的TM结构域相互作用非常接近。这些结果将有助于确定膜蛋白折叠中结构-功能关系的关键原则，并在更长的范围内，为这些因素如何在疾病状态下变得异常提供洞察力。

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.