Microstructural Heterogeneity in Membranes

受调控的膜融合对许多细胞过程和脂膜病毒的生命周期是必不可少的。 例如艾滋病毒、流感和埃博拉病毒。参与神经递质释放的几种蛋白质(“融合机器”) 和包膜病毒感染已被鉴定和结构特征。尽管如此，这些蛋白质是如何 催化融合还没有完全被理解。Lentz实验室研究与融合相关的脂类重排 在合成膜之间。该方法首先定义了纯脂系统中的这些重排。 然后问融合蛋白如何促进它们。核聚变需要密切接触 膜，这是用惰性聚合物聚乙二醇(PEG)诱导的。脂类之间的融合 聚乙二醇聚合囊泡至少是一个三步过程(接触双分子层D“柄”)。 中间D“隔膜”中间D孔)，模拟生物膜融合。Lentz集团 利用片状脂相的力学性质，计算了该体系的自由能反应曲线。 “茎”的融合机制，并表明它与他们独特的研究渗出动力学是一致的。 实验和计算表明，弯曲的脂单分子膜和缺陷之间的自由能 非片层和片层结构(疏水间隙)主导融合过程。多数 研究人员一直专注于弯曲能来解释核聚变。核心假设是核聚变 蛋白质不仅通过改变弯曲能催化融合，而且在很大程度上通过稳定疏水性来催化融合 空隙。为了验证这一假设，该项目将解决七个具体目标： 1]比较不同的弯曲诱导性脂质分配或促进弯曲的脂质结构的能力，以及 2)改变融合反应机制；3)确定感染阻断突变是否在 HIV的膜跨域改变了合成的膜跨域多肽的结构， 改变膜结构，并改变这种多肽对融合的影响；4]确定在 流感病毒的一个关键区域(“融合”肽)会改变合成的融合肽的结构，b} 膜结构，以及c)该肽对融合的影响；5]确定神经递质是否- 神经元融合蛋白(突触素)跨膜区域的释放阻断突变改变 合成膜跨域多肽的结构，b}膜结构，以及c}的作用 6]通过电子显微镜确定接触点是否形成融合孔 通过神经元融合蛋白保持接触的膜之间；和决定神经元能力的 钙结合蛋白(Synaptopagmin)扰动并触发模型膜之间的融合

Regulated membrane fusion is essential to many cell processes and to the life cycle of lipid-sheathed viruses such as HIV, Influenza, and Ebola. Several proteins ("fusion machines") involved in neurotransmitter release and enveloped viral infection have been identified and characterized structurally. Still, how these proteins catalyze fusion is not fully understood. The Lentz lab studies lipid rearrangements associated with fusion between synthetic membranes. The approach is first to define these rearrangements in pure lipid systems and then to ask how fusion proteins might promote them. Fusion requires close contact between membranes, which is induced using the inert polymer poly(ethylene glycol) (PEG). Fusion between lipid vesicles aggregated by PEG is shown to be minimally a three-step process (contacted bilayers D "stalk" intermediate D "diaphragm" intermediate D pore) that mimics biomembrane fusion. The Lentz group calculated, using the mechanical properties of lamellar lipid phases, the free energy reaction profile of this "stalk" fusion mechanism and showed it to be consistent with their unique studies effusion kinetics. Experiments and calculations show that the free energies of bent lipid monolayers and of defects between non-lamellar and lamellar structures (hydrophobic interstices) dominate the fusion process. Most researchers have focused on the bending energy to explain fusion. The Central Hypothesis is that fusion proteins catalyze fuSion not just by altering bending energy but in good measure by stabilizing hydrophobic interstices. To test this hypothesis, the project will address seven Specific Aims: 1] Compare the abilities of different bend-inducing lipids to partition into or promote bent lipid structures, and 2] alter the fusion reaction mechanism; 3] Determine whether an infection-blocking mutation in the membrane spanning domain of HIV alters the structure of a synthetic membrane spanning domain peptide, alters membrane structure, and alters the effect of this peptide on fusion; 4] Determine whether mutations in a key region of Influenza virus (the "fusion" peptide) alter a} the structure of a synthetic fusion peptide, b} membrane structure, and c} the effect of this peptide on fusion; 5] Determine whether neurotransmitter- release-blocking mutations in the membrane-spanning region of a neuronal fusion protein (syntaxin) alter a} the structure of a synthetic membrane spanning domain peptide, b} membrane structure, and c} the effect of this peptide on fusion; 6] Determine by electron microscopy whether fusion pores form at the point of contact between membranes held in contact by neuronal fusion proteins; and 7] Determine the ability of a neuronal calcium-binding protein (synaptotagmin) to perturb, and trigger fusion between, model membranes brought