Conformational transitions of membrane-spanning peptides

跨膜肽的构象转变 嵌入在所有活细胞的膜中，膜蛋白是内部和外部世界之间的分子联系。这些蛋白质代表了所有人类基因的20-30%，以及FDA在过去十年中批准的70%的药物靶标，它们调节生物脂质双层的分子交通和信息流。鉴于膜蛋白中的关键突变是许多人类疾病的原因，理解和控制其结构的努力在基础和应用研究中具有极大的兴趣。 膜蛋白的突变可以被认为是生物物理事件，其不仅影响对功能至关重要的跨膜螺旋的包装和静电相互作用，而且影响给定蛋白质片段与细胞的脂质双层环境的相容性。 因此，我们的研究重点是构成膜蛋白基本成分的蛋白质片段。在NSERC资助的研究中，本申请是一个更新，我们已经推进了分子设计，化学合成以及生物化学和生物物理方法的使用，以解开“细胞如何选择给定序列进行膜插入，接收脂质环境如何起作用以稳定插入片段，以及单个氨基酸的变化如何彻底改变蛋白质的生物命运。在此基础上，我们建议设计和化学合成几个系列的组成相同的肽，以产生相同的组成序列，但不同的位置和平衡的疏水性和极性残基。我们将通过生物化学技术如凝胶电泳和圆二色光谱来评估肽-脂质相互作用。 与此同时，我们将与Gunnar von Heijne教授（斯德哥尔摩大学）合作，他是膜蛋白结构方面的世界专家，我们将使用生物测定法来确定相应肽序列在体内的插入倾向。 然后，我们将应用我们的研究结果来评估类似的系统性序列变异的天然跨膜序列的单跨膜蛋白。 这项研究将确定膜蛋白折叠和功能的结构-功能关系的关键原则。我们的总体结果将提供丰富的基本信息，肽和蛋白质在膜环境中的相互作用的性质。

Conformational transitions of membrane-spanning peptides Embedded in the membranes of all living cells, membrane proteins are the molecular links between the inside and outside world. These proteins, which represent 20-30% of all human genes, and 70% of drug targets approved by the FDA in the past decade, regulate molecular traffic and information flow across biological lipid bilayers. Given that critical mutations in membrane proteins underlie the causes of many human diseases, efforts to understand and control their structures are of great interest in basic and applied research. Mutations in membrane proteins can be regarded as biophysical events that influence not only packing and electrostatic interactions of membrane-spanning helices critical for function, but as well the compatibility of a given protein segment with the lipid bilayer environment of the cell. Our research thus focuses on the protein segments that constitute the basic components of membrane proteins. Under NSERC-funded research, for which the present application is a renewal, we have advanced the use of molecular design, chemical synthesis, and biochemical and biophysical approaches to unravel the code' as to how a given sequence is selected by a cell for membrane insertion, how the receiving lipid environment acts to stabilize the inserted segments, and ultimately how a change in a single amino acid can drastically alter a protein's biological fate. Building on this foundation, we propose to design and chemically synthesize several series of compositionally identical peptides to produce sequences of identical composition, but with varying placement and balance of hydrophobic and polar residues. We will assess peptide-lipid interactions by biochemical techniques such as gel electrophoresis and circular dichroism spectroscopy. In parallel, we will collaborate with Prof. Gunnar von Heijne (Stockholm University) a world expert in membrane protein structure to use a biological assay to determine the insertion propensity of the corresponding peptide sequences in vivo. We will then apply our findings to assess similar systematic sequence variations in the native transmembrane sequence of a single-spanning membrane protein. This research will define key principles about structure-function relationships in membrane protein folding and function. Our overall results will provide a wealth of fundamental information as to the nature of peptide- and protein interactions in membrane environments.