Novel Lectins from Bauhinia with Differential N- Glycan Binding Profiles

Abstract

The specific interaction of lectins with carbohydrates and glycoconjugates grants these proteins a distinct ability to decode the glycocode. Essential for various biological processes in all organisms, this carbohydrate-binding activity also establishes lectins as valuable tools in fields such as glycomics, medicine, and biotechnology. Considering that the discovery of novel lectins with unique binding profiles is particularly relevant, this study investigated the binding specificity of two lectins extracted from Bauhinia seeds toward simple sugars, N-glycans and O-glycans. The combination of agglutination-inhibition assays and glycan arrays revealed subtle differences in the binding of the lectins to galactosides and glycans containing specific motifs, such as LewisX, LacdiNAc, and fucosylated LacdiNAc. Despite slight differences in carbohydrate-binding patterns, both lectins showed similar results in toxicity assays using Artemia salina nauplii and cytotoxicity assays on cancer cell lines, with neither lectin exhibiting significant toxicity. Additionally, both lectins demonstrated low cytotoxicity toward HeLa (cervical adenocarcinoma), HT1080 (fibrosarcoma), and NHDF (normal fibroblasts), even at concentrations up to 125 μg/mL. Analysis of the partial amino acid sequences of these lectins revealed conserved residues compared to other lectins of the genus, as well as secondary structure conformations similar to those of other legume lectins. This research represents a significant advancement in the understanding of lectins from the genus Bauhinia, and future structural studies could further elucidate the interactions of these proteins with their ligands, providing fundamental insights into their biological functions and paving the way toward potential applications.

Figure 1

Glycan array screening of BRL (A) and BBL (B). Each histogram represents the mean RFU (relative fluorescence unit) values for four spots with SD (standard deviation) of the mean. Only select glycan structures are represented and grouped considering their terminal epitopes: LDNF (red bars), Lewis X (blue bars) and LDN (green bars). Glycan structures included in the microarray are available in Figure S1 and full data from microarray experiments in Figure S2.

Figure 2

Sequence alignment of BRL and BBL with other Cercidoideae subfamily lectins. Residues that constitute the carbohydrate recognition domain (*) and metal-binding site (#). The relative accessibility of each residue is rendered as blue-colored boxes shown in the last line of each block. Higher intensity of blue reflects better accessibility.