Shirai Tsuyoshi, Watanabe Yasuharu, Lee Min-sub, Ogawa Tomohisa, Muramoto Koji
Department of Bioscience, Nagahama Institute of Bio-science and Technology, and JST-BIRD, Tamura, Nagahama, Japan.
J Mol Biol. 2009 Aug 14;391(2):390-403. doi: 10.1016/j.jmb.2009.06.027. Epub 2009 Jun 12.
The crystal structure of the L-rhamnose-binding lectin CSL3 was determined to 1.8 A resolution. This protein is a component of the germline-encoded pattern recognition proteins in innate immunity. CSL3 is a homodimer of two 20 kDa subunits with a dumbbell-like shape overall, in which the N- and C-terminal domains of different subunits form lobe structures connected with flexible linker peptides. The complex structures of the protein with specific carbohydrates demonstrated the importance of the most variable loop region among homologues for the specificity toward oligosaccharides. CSL3 and Shiga-like toxin both use Gb(3) as a cellular receptor to evoke apoptosis. They have very different overall architecture but share the separation distance between carbohydrate-binding sites. An inspection of the structure database suggested that the pseudo-tetrameric structure of CSL3 was unique among the known lectins. This architecture implies this protein might provide a unique tool for further investigations into the relationships between architecture and function of pattern recognition proteins.
L-鼠李糖结合凝集素CSL3的晶体结构分辨率达到了1.8埃。该蛋白是先天免疫中种系编码模式识别蛋白的一个组成部分。CSL3是由两个20 kDa亚基组成的同型二聚体，整体呈哑铃状，其中不同亚基的N端和C端结构域形成叶状结构，通过柔性连接肽相连。该蛋白与特定碳水化合物的复合物结构表明，同源物中最可变的环区对于寡糖特异性的重要性。CSL3和志贺样毒素都利用Gb(3)作为细胞受体来引发细胞凋亡。它们的整体结构非常不同，但碳水化合物结合位点之间的间隔距离相同。对结构数据库的检查表明，CSL3的假四聚体结构在已知凝集素中是独特的。这种结构意味着该蛋白可能为进一步研究模式识别蛋白的结构与功能之间的关系提供一个独特的工具。
