Wyss D F, Withka J M, Knoppers M H, Sterne K A, Recny M A, Wagner G
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
Biochemistry. 1993 Oct 19;32(41):10995-1006. doi: 10.1021/bi00092a008.
Human CD2, a glycosylated transmembrane receptor found on all T-lymphocytes, plays a key role in facilitating cellular adhesion between T-cells and target cells or antigen-presenting cells by binding to its counter receptor CD58 (LFA-3) present on the surface of those cells. All CD2 adhesion functions are localized within the amino-terminal 105-residue domain, which contains a single high mannose N-glycan required for maintaining both the conformational stability and CD58 binding properties of the glycoprotein. In order to better understand the structural basis for CD2-CD58-mediated adhesion and the critical role of the carbohydrate moiety in maintaining the functional stability of the molecule, we have determined the secondary structure of the N-glycosylated adhesion domain of human CD2 (hu-sCD2(105)) using NMR spectroscopy. Most of the 1H resonance assignments have been obtained from 1H-1H homonuclear 2D NMR spectra, which were further extended by applying 1H-15N heteronuclear 2D experiments on a hu-sCD2(105) sample selectively labeled with [15N]lysine. Thus, 98% of all backbone 1H resonances and over 80% of all side chain 1H resonances have been assigned. An overall topology characteristic of an immunoglobulin variable domain is observed, which consists of two beta-sheets comprised of three (residues 16-20, 67-71, and 60-63) and five (residues 94-103, 80-86, 32-37, 45-47, and 53-55) antiparallel beta-strands, respectively, with a hydrophobic core sandwiched between them. A ninth beta-strand (residues 7-12) makes parallel contacts to the carboxy-terminal beta-strand. NOEs between the N-linked glycan and the protein have tentatively been identified.
人CD2是一种在所有T淋巴细胞上发现的糖基化跨膜受体，通过与这些细胞表面存在的配对受体CD58（淋巴细胞功能相关抗原3）结合，在促进T细胞与靶细胞或抗原呈递细胞之间的细胞黏附中起关键作用。所有CD2黏附功能都定位于氨基末端105个残基的结构域内，该结构域包含一个维持糖蛋白构象稳定性和CD58结合特性所需的单个高甘露糖N - 聚糖。为了更好地理解CD2 - CD58介导的黏附的结构基础以及碳水化合物部分在维持分子功能稳定性中的关键作用，我们使用核磁共振光谱法确定了人CD2的N - 糖基化黏附结构域（hu - sCD2(105)）的二级结构。大部分1H共振归属是通过1H - 1H同核二维核磁共振光谱获得的，通过对用[15N]赖氨酸选择性标记的hu - sCD2(105)样品进行1H - 15N异核二维实验进一步扩展。因此，已归属了所有主链1H共振的98%和所有侧链1H共振的80%以上。观察到免疫球蛋白可变结构域的总体拓扑特征，它由两个β - 折叠组成，分别由三条（残基16 - 20、67 - 71和60 - 63）和五条（残基94 - 103、80 - 86、32 - 37、45 - 47和53 - 55）反平行β - 链组成，中间夹着一个疏水核心。第九条β - 链（残基7 - 12）与羧基末端β - 链形成平行接触。已初步鉴定了N - 连接聚糖与蛋白质之间的核Overhauser效应。
