Structure-Function Studies of Lipid Binding Proteins

;​R o o t E n t y F Ek 9 @ C o m p o b j b W o r d d o c u m e n t O b j e c t P O O l Ek 9 Ek 9​F Microsoft Word 6.0文档MSWordDoc。6;Oh +' 0 $ H l D H R:\WWUSER\TEMPLATE\NORMAL。DOT玛西娅·斯坦伯格玛西娅·斯坦伯格@ 9 @ e = e j j j j j j j j B # $ TB j B j j j j ~ j j j j j 7 9506088 Bernlohr就像有载体蛋白起溶解和在循环系统中传递疏水分子，在细胞内发现了类似的蛋白质家族。这些蛋白质被称为脂质结合蛋白，负责细胞内疏水配体的增溶和递送。脂质结合蛋白家族的成员以或多或少的组织特异性方式表达，因此根据其表达的细胞类型来命名每个成员。脂质结合蛋白与脂肪酸和类维生素a结合最为密切，尽管与血红素和溶血磷脂等分子也存在一些微弱的联系。尽管原生序列具有广泛的可变性，但通过多维核磁共振和X射线晶体学确定的家族成员的三维结构显着重叠。所有脂质结合蛋白的独特特征是存在一个内部充满水的空腔，作为β桶折叠基序内的配体结合域。在腔内，蛋白质与配体之间形成l:l复合物。一旦进入，配体就与外部环境隔离，并沿着结合域的一面壁牢牢地固定住。尽管在腔内发现了与蛋白质结合的配体，但没有明显的配体进出位点。一个大的充满水的空腔作为配体结合域，直观上似乎与蛋白质的目的相矛盾。如果蛋白质能促进不溶于水的脂质的溶解，为什么要把它们包裹在一个充满水的空腔里呢？配体是如何进出腔体的？控制蛋白质结构和脂质结合的热力学因素是什么？什么决定配体结合特异性？这个项目的目标是从分子的角度理解脂肪细胞脂质结合蛋白对配体结合的影响。长期目标是设计这种分子，使其作为一种疏水配体载体，能够与大量难溶性分子（如环境致癌物和诱变剂）高度亲和结合。为了实现这些目标，需要更全面地了解蛋白质脂肪酸相互作用的基础。不易溶于水的分子在生物系统中构成特殊问题。水溶性生物分子，如糖和氨基酸，很容易在水空间中扩散，而生物系统中的水不溶性化合物必须携带在蛋白质上。这些研究的重点是最常见的疏水配体载体蛋白，脂质结合蛋白。特别是P.I.详细研究了脂肪细胞脂质结合蛋白。这种蛋白质是50多种不同蛋白质的原型，所有这些蛋白质都有助于生物系统中疏水化合物的增溶。脂肪细胞脂质结合蛋白与长链脂肪酸具有高亲和力和选择性。蛋白质的X层晶体结构已被高分辨率解决，并揭示了令人惊讶的发现，疏水，不溶性脂肪酸结合在一个大的中心，充满水的空腔。不溶性分子在充满水的空腔中结合，这在直觉上是矛盾的。通过改变结合区域的氨基酸和测量蛋白质脂质相互作用的特性，pi正试图理解控制这种不溶性分子结合的“规则”。一旦确定了这些规则，就可以设计出能够结合疏水化合物的新蛋白质，例如在生物圈中积累的环境污染物和致癌物。*** @ @；​如果我是你，我是你，我是你，我是你，我是你。

; R o o t E n t r y F Ek 9 @ C o m p O b j b W o r d D o c u m e n t O b j e c t P o o l Ek 9 Ek 9 F Microsoft Word 6.0 Document MSWordDoc Word.Document.6 ; Oh +' 0 $ H l D h R:\WWUSER\TEMPLATE\NORMAL.DOT marcia steinberg marcia steinberg @ 9 @ e = e j j j j j j j B L # $ T 4 B j B j j j j ~ j j j j 7 9506088 Bernlohr Just as there are carrier proteins that function to solubilize and deliver hydrophobic molecules in the circulatory system, there exists an analogous family of proteins that are found intracellularly. These proteins, which have been termed the lipid binding proteins, are responsible for the intracellular solubilization and delivery of hydrophobic ligands within a cell. The members of the lipid binding protein family are expressed in a more or less tissue specific manner, hence the naming of each member based upon the cell type it is expressed in. The lipid binding proteins bind most avidly to fatty acids and retinoids although some weak association with such molecules as heme and lysophospholipids does occ ur. Despite the wide variability in primary sequence, the three dimensional structure of the family members, as determined by multidimensional NMR and X ray crystallography, are remarkably superimposable. The unique feature of all the lipid binding proteins is the presence of an internal water filled cavity that serves as the ligand binding domain within a beta barrel folding motif. A l:l complex is formed between the proteins and the ligand within the cavity. Once inside, the ligand is sequestered from the external milieu and is held rigidly along one wall of the binding domain. Despite the finding of the ligand bound to the protein within the cavity, there is no obvious site for ligand entry/exit. A large water filled cavity that serves as the ligand binding domain seems intuitively contradictory to the purpose of the proteins. If the proteins facilitate the solubilization of water insoluble lipids why enclose them in a cavity filled with water? How do ligands enter and exit the cavity? What are the thermodynamic factors which govern protein structure and lipid binding? What determines the ligand binding specificity? The goals for this project are to understand in molecular terms the factors which contribute to ligand binding by the adipocyte lipid binding protein. A long term goal is to engineer the molecule to be of general use as a hydrophobic ligand carrier capable of high affinity association with a wide number of poorly soluble molecules such as environmental carcinogens and mutagens. To achieve these goals a more complete understanding of the basis for protein fatty acid interaction is needed. %%% Molecules that cannot dissolve readily in water pose special problems in biological systems. While water soluble biological molecules such as sugars and amino acids readily diffuse throughout aqueous space, water insoluble compounds in biological systems must be carried on proteins. The focus of these studies is on the most common type of hydrophobic ligand carrier proteins, the lipid bindin g proteins. In particular the P.I. studies in detail the adipocyte lipid binding protein. This protein is the prototype for over 50 different proteins, all of which facilitate the solubilization of hydrophobic compounds in biological systems. The adipocyte lipid binding protein associates with high affinity and selectivity with long chain fatty acids. The X pay crystal structure of the protein has been solved to high resolution and reveals the surprising finding that the hydrophobic, insoluble fatty acids are bound within a large central, water filled cavity. The binding of insoluble molecules into a water filled cavity is intuitively contradictory. By altering the amino acids in the binding domain and by measuring the properties of the protein lipid interactions, the P.I. is trying to understand the "rules" which govern the binding of such insoluble molecules. Once such rules are identified, new proteins might be engineered that are capable of binding hydrophobic compounds such as environmental pollutants and carcinogens that accumulate in the biosphere. *** @ @ ; S u m m a r y I n f o r m a t i o n (