Detection & Analysis of Intact Glycosylated Biomolecules.
Lectins can be immobilized onto a wide range of solid supports to create glycoselective bioaffinity matrices. This enables the ability of lectins to recognize and bind specific glycans in situ to be exploited for the separation and isolation of glycosylated biomolecules and their glycoforms on the basis of the glycans they display. This overcomes the limitations of traditional separations tools and techniques that separate biomolecules on the basis of their size, charge status or hydrophobicity/hydrophilicity and so are not glycoselective.
Lectins are proteins that are capable of recognizing and binding to specific glycan structures displayed on biomolecules. In nature Lectins mediate a broad range of biological processes through interaction with glycans and glycosylated biomolecules.
Lectins - GlycoSeLective Tools for the Life Sciences
Incompatibility with Recombinant Production Methods: Like many eukaryotic proteins plant lectins are not amenable to recombinant expression in Escherichia coli. Expression often results in low yields or expression as insoluble protein. This is further complicated by the fact that plant and eukaryotic lectins often have complex structures being comprised of multiple different subunits (isolectins) and they can carry post-translation modifications including glycosylation (e.g. ECL). Incompatibility with recombinant approaches also precludes optimization of performance via mutagenesis strategies.
Inconsistent Quality & Performance: The quality and performance of plant lectins can vary from batch to batch and from one supplier to another. Plant lectins are usually produced by isolation from source plant material and the quality of the products obtained depends on the isolation procedures used and on the quality of the starting material which can be highly variable.
Lack of Selectivity: Plant derived lectins are often reported to bind to a range of different glycan structures and so lack the selectivity required for many applications.
While current commercially available plant and eukaryotic lectins offer many advantages as glycoselective tools for the analysis and isolation of glycosylaed biomolecules they also exhibit a number of significant limitations that have restricted their wider utility.
Erythrina Cristagali Lectin (ECL) - a galactophilic plant lectin. The lectin has two identical subunits with one carbohydrate (yellow) binding site per subunit. The lectin itself is glycosylated with one glycan per subunit (red)
Glycoselective Isolation of Glycosylated Biomolecules.
Current Glycoanalytical Methods: These typically require the initial release, isolation and labelling of glycans from biomolecules. The resulting pool of labeled glycans is then separated and the constituent glycans structures identified and quantified using HPLC and MS based approaches. The requirement for glycan release means that biologically relevant information relating to the occupancy of different glycosylation sites can be lost precluding full glycoprotein characterisation. This is particularly relevant for glycoproteins that contain multiple glycosylation sites.
Recombinant Prokaryotic Lectins (RPLs): overcome the limitations of current plant and eukaryotic lectins. They exhibit superior performance, quality and compatibility with simple and readily scalable production methods enabling their use for all application scales.
Production is Not Readily Scalable: The incompatibility of plant and eukaryotic lectins with recombinant production methods, and the resulting necessity to isolate from source material, limits the scalability of their production which restricts their use to small analytical scale applications.
The ability of lectins to bind to specific glycan structures in situ makes them valuable tools that enable simple and fast detection and analysis of intact glycosylated biomolecules. This is in contrast to traditional glycoanalytical methods that are often highly complex, labour intensive and time consuming in addition to requiring highly trained personnel. Lectins can be used in a diverse range of formats to meet specific analytical needs.
Limitations of Plant & Eukaryotic Lectins
Since their initial discovery Lectins have found widespread and diverse applications but with the rapid growth of Glycoscience Lectins have become valuable tools for the detection, analysis and isolation of glycosylated biomolecules. Lectins offer many advantages over other glycoanalytical and chromatographic approaches.