Department of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-Ku, Tokyo, 113-0033, Japan.
Faculty of Pharmaceutical Sciences, Tohoku Medical and Pharmaceutical University, Miyagi, 981-8558, Japan.
Curr Top Microbiol Immunol. 2020;429:147-176. doi: 10.1007/82_2019_181.
Carbohydrate recognition is an essential function occurring in all living organisms. Lectins are carbohydrate-binding proteins and are classified into several families. In mammals, Ca-dependent C-type lectins, such as β-galactoside-binding galectin and sialic acid-binding siglec, play crucial roles in the immune response and homeostasis. C-type lectins are abundant and diverse in animals. Their immunological activities include lymphocyte homing, pathogen recognition, and clearance of apoptotic bodies. C-type lectin domains are composed of 110-130 amino acid residues with highly conserved structural folds. Remarkably, individual lectins can accept a wide variety of sugar ligands and can distinguish subtle structural differences in closely related ligands. In addition, several C-type lectin-like proteins specifically bind to carbohydrate ligands in Ca-independent ways. The accumulated 3D structural evidence clarifies the unexpected structural versatility of C-type lectins underlying the variety of ligand binding modes. In this issue, we focus on the structural aspects of carbohydrate recognition mechanisms of C-type lectins and C-type lectin-like proteins.
碳水化合物识别是所有生物中普遍存在的基本功能。凝集素是一种碳水化合物结合蛋白，可分为几个家族。在哺乳动物中，Ca 依赖性 C 型凝集素，如 β-半乳糖苷结合的半乳糖凝集素和唾液酸结合的 Siglec，在免疫反应和动态平衡中发挥着至关重要的作用。C 型凝集素在动物中丰富多样。它们的免疫活性包括淋巴细胞归巢、病原体识别和清除凋亡体。C 型凝集素结构域由 110-130 个氨基酸残基组成，具有高度保守的结构折叠。值得注意的是，单个凝集素可以接受多种糖配体，并能区分密切相关配体中细微的结构差异。此外，一些 C 型凝集素样蛋白以 Ca 非依赖性方式特异性结合碳水化合物配体。积累的 3D 结构证据阐明了 C 型凝集素在各种配体结合模式下意想不到的结构多功能性。在本期中，我们重点介绍 C 型凝集素和 C 型凝集素样蛋白的碳水化合物识别机制的结构方面。
