CELL SURFACE CARBOHYDRATE RECOGNITION BY C-TYPE LECTINS

C 型凝集素对细胞表面碳水化合物的识别

• 批准号: 6329752
• 负责人: William I Weis
• 金额: $ 28.03万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-12-01 至 2002-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6329752
• 关键词: X ray crystallography; acidity /alkalinity; binding sites; calcium ion; carbohydrate receptor; carbohydrate structure; chemical binding; complement pathway; crystallization; endocytosis; immunity; lectin; ligands; mannose; mucins; mutant; oligosaccharides; protein isoforms; protein structure function; selectins; stereochemistry

The goal of this proposal is to understand the structural basis of specificity and mechanism in C-type (Ca/2+-dependent) lectins that function in the innate and adaptive immune responses, using x-ray crystallography as the principal tool. 1) Mannose-binding proteins (MBPs) recognize oligosaccharide structures present on pathogenic surfaces and trigger killing of these organisms by activating the complement system. The ability of MBPs to distinguish foreign from self depends on high avidity, multivalent binding to pathogenic cells but not endogenous glycoconjugates. As multivalent binding bends on spacing of binding sites and recognition of ligands presented in particular orientations, structures of MBP oligomers and MBP mutants that bind to ligands in alternative orientations will be examined. 2) The mannose receptor or macrophages and dendritic cell endocytoses pathogens and potentially harmful glycoconjugates, leading to their destruction and processing for antigen presentation. Structures of a single carbohydrate-recognition domain (CRD) will be determined in complex with ligands to probe the unique features of ligand recognition by this receptor. The structure of a receptor fragment containing two CRDs will be determined in order to visualize the spacing of binding sites and its effects on multivalenty. Ca/2+ binding to CRD-4 will be examined by fluorescence and crystallographic methods, to probe the molecular basis of the pH-induced loss of Ca/2+ and sugar affinity in the endosome. Mutants of MBP engineered to mimic the pH transition of endocytic receptors such as the mannose receptor, will also be examined. 3) The selectin cell adhesion molecules mediate the first step in leukocyte targeting to lymphoid tissues and sites of inflammation. The structures of MBP/selectin chimeras that mimic the binding of selectins will be determined in complex with selectin ligands, as will the structure of an L-selectin fragment containing the lectin and EGF-like domains.

该提议的目的是了解 C型（Ca/2+依赖性）凝集素中的特异性和机制 使用X射线在先天和适应性免疫反应中发挥作用 晶体学作为主要工具。 1）甘露糖结合蛋白（MBP）识别寡糖结构 通过致病表面和触发这些生物杀死这些生物 激活补体系统。 Mbps区分的能力 来自自我的外国依赖于高潮，多价结合到 致病细胞，但不是内源性糖缀合物。作为多价 结合弯曲对结合位点的间距和配体的识别 MBP低聚物和MBP的结构特别取向 将检查与配体在替代方向上结合的突变体。 2）甘露糖受体或巨噬细胞和树突状细胞内吞作用 病原体和潜在有害的糖缀合物，导致其 抗原表现的破坏和加工。 A的结构 单个碳水化合物识别域（CRD）将在复杂中确定 使用配体来探测配体识别的独特特征 受体。包含两个CRD的受体片段的结构将是 确定为了可视化绑定位点及其的间距 对多价的影响。 CA/2+与CRD-4的结合将通过 荧光和晶体学方法，以探测分子基础 pH诱导的内体中Ca/2+和糖亲和力的损失。突变体 MBP的设计，以模仿内吞受体的pH过渡 作为甘露糖受体，也将被检查。 3）选择素细胞粘附分子介导了第一步 白细胞靶向淋巴组织和炎症部位。这 MBP/Selectin Chimeras的结构，模仿Selectins的结合 将与Selectin配体复杂确定，结构也将 含有凝集素和EGF样结构域的L-选择素片段的。