Maranhão Paulo A C, Teixeira Claudener S, Sousa Bruno L, Barroso-Neto Ito L, Monteiro-Júnior José E, Fernandes Andreia V, Ramos Marcio V, Vasconcelos Ilka M, Gonçalves José F C, Rocha Bruno A M, Freire Valder N, Grangeiro Thalles B
Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, 60440-900, Brazil.
Faculdade de Filosofia Dom Aureliano Matos, Universidade Estadual do Ceará, Av. Dom Aureliano Matos, 2060, Limoeiro do Norte, CE, 62930-000, Brazil.
Phytochemistry. 2017 Jul;139:60-71. doi: 10.1016/j.phytochem.2017.04.007. Epub 2017 Apr 14.
The genus Swartzia is a member of the tribe Swartzieae, whose genera constitute the living descendants of one of the early branches of the papilionoid legumes. Legume lectins comprise one of the main families of structurally and evolutionarily related carbohydrate-binding proteins of plant origin. However, these proteins have been poorly investigated in Swartzia and to date, only the lectin from S. laevicarpa seeds (SLL) has been purified. Moreover, no sequence information is known from lectins of any member of the tribe Swartzieae. In the present study, partial cDNA sequences encoding L-type lectins were obtained from developing seeds of S. simplex var. grandiflora. The amino acid sequences of the S. simplex grandiflora lectins (SSGLs) were only averagely related to the known primary structures of legume lectins, with sequence identities not greater than 50-52%. The SSGL sequences were more related to amino acid sequences of papilionoid lectins from members of the tribes Sophoreae and Dalbergieae and from the Cladratis and Vataireoid clades, which constitute with other taxa, the first branching lineages of the subfamily Papilionoideae. The three-dimensional structures of 2 representative SSGLs (SSGL-A and SSGL-E) were predicted by homology modeling using templates that exhibit the characteristic β-sandwich fold of the L-type lectins. Molecular docking calculations predicted that SSGL-A is able to interact with D-galactose, N-acetyl-D-galactosamine and α-lactose, whereas SSGL-E is probably a non-functional lectin due to 2 mutations in the carbohydrate-binding site. Using molecular dynamics simulations followed by density functional theory calculations, the binding free energies of the interaction of SSGL-A with GalNAc and α-lactose were estimated as -31.7 and -47.5 kcal/mol, respectively. These findings gave insights about the carbohydrate-binding specificity of SLL, which binds to immobilized lactose but is not retained in a matrix containing D-GalNAc as ligand.
斯沃茨木属是斯沃茨木族的成员，该族的属构成了蝶形花亚科豆类植物早期分支之一的现存后代。豆类凝集素是植物来源的结构和进化相关的碳水化合物结合蛋白的主要家族之一。然而，这些蛋白质在斯沃茨木属中研究较少，迄今为止，仅纯化了光果斯沃茨木种子中的凝集素（SLL）。此外，关于斯沃茨木族任何成员的凝集素，尚无序列信息。在本研究中，从大花单叶豆发育中的种子中获得了编码L型凝集素的部分cDNA序列。大花单叶豆凝集素（SSGLs）的氨基酸序列与豆类凝集素已知的一级结构平均相关性较低，序列同一性不超过50 - 52%。SSGL序列与槐族和黄檀族成员以及克拉迪蒂斯和瓦泰雷奥类分支的蝶形花凝集素的氨基酸序列关系更密切，这些与其他类群共同构成了蝶形花亚科的第一个分支谱系。使用具有L型凝集素特征性β-三明治折叠的模板，通过同源建模预测了2种代表性SSGL（SSGL-A和SSGL-E）的三维结构。分子对接计算预测SSGL-A能够与D-半乳糖、N-乙酰-D-半乳糖胺和α-乳糖相互作用，而由于碳水化合物结合位点的2个突变，SSGL-E可能是一种无功能的凝集素。通过分子动力学模拟，随后进行密度泛函理论计算，SSGL-A与GalNAc和α-乳糖相互作用的结合自由能分别估计为-31.7和-47.5 kcal/mol。这些发现为SLL的碳水化合物结合特异性提供了见解，SLL与固定化乳糖结合，但不保留在含有D-GalNAc作为配体的基质中。
