Department of Microbiology and Immunology, University of Maryland School of Medicine, UMB, and Institute of Marine and Environmental Technology, Columbus Center, Baltimore, MD, USA.
Methods Mol Biol. 2020;2132:225-239. doi: 10.1007/978-1-0716-0430-4_23.
F-type lectins (FTLs) are characterized by a fucose recognition domain (F-type lectin domain; FTLD) that displays a novel jellyroll fold ("F-type" fold) and unique carbohydrate- and calcium-binding sequence motifs. This novel lectin family comprises widely distributed proteins exhibiting single, double, or greater multiples of the FTLD, either tandemly arrayed or combined with other structurally and functionally distinct domains. Further, differences in carbohydrate specificity among tandemly arrayed FTLDs present in any FTL polypeptide subunit, together with the expression of multiple FTL isoforms in a single individual supports a striking diversity in ligand recognition. Functions of FTLs in self/nonself recognition include innate immunity, fertilization, microbial adhesion, and pathogenesis, among others, revealing an extensive structural/functional diversification. The taxonomic distribution of FTLDs is surprisingly discontinuous, suggesting that this lectin family has been subject to secondary loss, lateral transfer, and functional co-option along evolutionary lineages.
F 型凝集素（FTLs）的特征在于其具有岩藻糖识别结构域（F 型凝集素结构域；FTLD），该结构域具有独特的卷曲螺旋折叠（“F 型”折叠）和独特的碳水化合物结合和钙结合序列基序。这个新型的凝集素家族包括广泛分布的蛋白质，这些蛋白质表现出单、双或更多的 FTLD 重复，要么串联排列，要么与其他结构和功能不同的结构域结合。此外，在任何 FTL 多肽亚基中串联排列的 FTLD 之间的碳水化合物特异性差异，以及在单个个体中表达多个 FTL 同工型，支持配体识别的显著多样性。FTLs 在自我/非自我识别中的功能包括先天免疫、受精、微生物黏附和发病机制等，揭示了广泛的结构/功能多样化。FTLD 的分类分布令人惊讶地不连续，这表明这个凝集素家族经历了次生缺失、侧向转移和功能协同进化。
