Literature review of lectins from mimosoideae subfamily (Leguminoseae): purification strategies, structural data and biological activities

Full text: Lectins are a group of proteins of nonimmune origin widely distributed in nature. These proteins recognize and bind specific carbohydrates found on the surfaces of cells and play a role in interaction and communication between cells, as well as interaction with glycoconjugates. Legume lectins are an extensive group with homogeneous physicochemical and structural properties, but very different biological activities. Inside the legume lectin group, most of the studies focus on the Papilionoideae subfamily, with the other two, Caesalpinioideae and Mimosoideae being significantly less explored in the literature. The focus of the present research is the Mimosoideae subfamily, the second largest in number of taxa, comprising four tribes (Mimoseae, Mimozygantheae, Acacieae and Ingeae) with about 3275 species and 79 genera, but with only about 14 lectins purified lectins, which depicts the lack of studies for this group. To date, researchers have reported on the purification, characterization and some biological activities of the genera Parkia, Leucaena, Caliandra, Archidendron, Anadenanthera, Albizia and Acacia. The applied methodology was based on search and filtering of papers in the literature with posterior data extraction and compilation. Based on their purification protocols, as well as physicochemical properties, Mimosoideae lectins are very heterogeneous lectins. These differences become even more evident when these proteins are analyzed from a structural point of view. Although we have a few purified lectins from this subfamily, the structural studies to this date only include lectins of the Acacia and Parkia genera, and these are shown to be remarkably distinct from one another. Despite the few studies, a wide variety of biological activities have been tested, e.g. inflammatory, anticancer, antibacterial, and antifungal. In this context, considering the number of taxa belonging to the subfamily Mimosoideae and the importance of its lectins, this study aimed to present an overview of the available literature reporting the purification, structure, and biological activities of these proteins. In this context, synchrotron beamlines can help in the definition of the structure of each lectin by allowing structural solving by X-ray crystallography and other techniques such as SAXS. Several lectins already had their crystal structure solved, and the combined data of several crystal structures assisted researchers in the definition of several structural and functional properties of these proteins, but some groups of proteins still need more studies in this line with Mimosoideae lectins being a prime example. (author)