MUTATIONAL APPROACHES TO INVESTIGATION OF PROTEIN STRUCTURE, FUNCTION & FOLDING

研究蛋白质结构、功能的突变方法

• 批准号: 6478962
• 负责人: Christopher James MCKNIGHT
• 金额: $ 5.36万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6478962
• 关键词: bacteria; biological products; biomaterials; biomedical resource; carbohydrates; immunology; infection; inflammation; lipids; lymphatic system; structural biology

Human CDI proteins are a family of norimajor histocompatibility complex (MHC) encoded transmembrane glycoproteins expressed in association with 02-microglobulin on the surface of antigen-presenting cells (APCs). Unlike the well known M[HC class I and class 11 proteins that present peptide antigens to T cells, the human group I CD1 proteins (CD1a, CD1b andCDlc) mediate specific T cell recognition of bacterial lipid and glycolipid antigens. Previous studies of mycobacteria specific T cells have identified two classes of CDI-restricted lipid antigens. These are the free mycolic acids, a family of cc-branched, 0-hydroxy long chain fatty acids, and the phosphatidylinositol-containing glycolipids including lipoarabinomannan (LAM) andthe phosphatidylinositol mannosides (PlMs). Mycohacterium leprae infection has recently revealed evidence for a third class of CDI restricted lipid antigens. The CDI proteins play a central role in the specific T cell recognition of foreign lipid antigens, but the molecular mechanisms underlying lipid antigen presentation are not known. During this past year, we have identified a novel CDI-restricted glycolipid antigen, glucose monomycolate (GM[M), which is allowing a systematic analysis of the structural features that determine its recognition by T cells. Analogues of GNM that differed substantially in their acyl chain lengths and other chemical features of the lipid moiety were recognized by T cells. In contrast, T cells demonstrated fine specificity for the carbohydrate portion ?of mycolyl glycolipids, even discriminating among carbohydrate isomers differing only in the orientation of a single hydroxyl group (e.g., only glucose and not mannose or galactose). In combination with recent studies of the crystal structure of CD1, these results provide strong support for a molecular model of antigen presentation in which the acyl chains of the antigen bind relatively nonspecifically within the deep, hydrophobic pocket of the CD1 protein, resulting in presentation of the hydrophilic elements of antigens for highly specific interactions with the T cell receptor.

人类 CDI 蛋白是一个主要组织相容性正常的家族 复合体（MHC）编码的跨膜糖蛋白表达于 与抗原呈递表面的 02-微球蛋白结合 细胞（APC）。 与众所周知的M[HC I类和11类 将肽抗原呈递给 T 细胞（人类 I 组）的蛋白质 CD1 蛋白（CD1a、CD1b 和 CDlc）介导特异性 T 细胞识别 细菌脂质和糖脂抗原。 以前的研究 分枝杆菌特异性 T 细胞已鉴定出两类 CDI 限制性脂质抗原。 这些是游离的霉菌酸， cc-支链、0-羟基长链脂肪酸家族，以及 含磷脂酰肌醇的糖脂包括 脂阿拉伯甘露聚糖（LAM）和磷脂酰肌醇甘露糖苷（PLMs）。 最近发现了麻风分枝杆菌感染的证据 第三类CDI限制性脂质抗原。 CDI 蛋白发挥着 T 细胞对外来脂质的特异性识别中发挥核心作用 抗原，但脂质抗原的分子机制 介绍尚不清楚。 在过去的一年里，我们确定了 一种新型 CDI 限制性糖脂抗原，葡萄糖单菌酸酯 （GM[M），它允许对结构进行系统分析 决定其被 T 细胞识别的特征。 GNM 类似物 它们的酰基链长度和其他方面有很大不同 T 细胞识别脂质部分的化学特征。 在 相比之下，T 细胞对碳水化合物表现出良好的特异性 部分 ? 菌基糖脂，甚至区分 碳水化合物异构体仅在单个方向上有所不同 羟基（例如，只有葡萄糖，没有甘露糖或半乳糖）。 在 结合最近对CD1晶体结构的研究，这些 结果为抗原的分子模型提供了强有力的支持 抗原的酰基链相对结合的呈现 非特异性地位于 CD1 的深层疏水口袋内 蛋白质，导致亲水元素的呈现 与 T 细胞受体高度特异性相互作用的抗原。