Strategies to obtain lectins from distinct sources

Abstract

Lectins are proteins or glycoproteins that bind specifically to mono, oligo or polysaccharides. They are important biotechnological tools and have been isolated from microorganisms, higher fungus, lichens, plants and animals. Different purification strategies are used to obtain pure lectins. It is important to approach the principles of each method to be used in protein purification before start to work in this important field. The initial purification step is the protein extraction followed by saline fractionation and dialysis. Hemagglutinating activity (HA) is the assay to follow each protocol step. The prepared sample is submitted to chromatographic methods, such as, affinity, ion exchange and molecular exclusion chromatographies to purify the lectins. High resolution techniques for instance the fast protein liquid chromatography (FPLC) and high pressure liquid chromatography (HPLC) are also used to obtain lectins with high purity. A large number of lectins characterized by specific techniques are available with different carbohydrate specificities. Lectins or lectin molecular forms have structural characteristics making them unique proteins. The pure molecules can contribute to unravel its structure, potential biological function, as well as biotechnological and biomedical uses. Lectins can have applications in different areas of knowledge; they can be used to explore cell surface, be applied as mitogenic, cytotoxic and antimicrobial agents, and also be used as antiproliferative molecules for cancer cells. These proteins may be useful in water treatment due to their coagulant and antibacterial properties. Insecticidal lectins with potential biotechnological application for control of agricultural pests have also been described. There are pitfalls in lectin purification; among them is the structural similarity between contaminant proteins or other lectin molecular forms promoting difficulties to the purification process. A common problem is to establish the ideal protocol that ensures high level of purity and good recovery in few steps.