The Combination of Lectin Affinity Chromatography, Gel Electrophoresis and Mass Spectrometry in the Study of Plant Glycoproteome: Preliminary Insights

The study of plant proteome is important because proteins and glycoproteins are involved in many crucial biological processes that could enhance the agronomical and nutritional value of crops and food products. The analysis of model organisms (e.g., Arabidopsis thaliana) is a popular means to aid in understanding many plant features. Proteomics has the potential to contribute to cereal science, mainly through the description of grain quality by elucidating the ways in which the genes are expressed during grain filling under particular environmental conditions. Since barley grain composition (i.e., its protein and glycoprotein analysis) is important for the brewing industry, human and animal nutrition, plant breeding or cultivar identification, the profiles of glycoproteins released from barley were one of the aims of this paper. This work combines affinity chromatography with 1D gel electrophoresis followed by mass spectrometry for the characterization of modified plant proteins. Lectin chromatography with Concanavalin A (ConA) was integrated to the procedure for the selective isolation of N-glycoproteins. For the verification of the universality of a chosen approach, proteins were extracted by deionized water from two different model plant materials—barley (Hordeum vulgare) and A. thaliana. Our attention was focused on the glycoproteins present in both barley grains and grains after the malting procedure and Arabidopsis seedlings. The proteins retained in an affinity column were separated by SDS-PAGE, excised, digested by trypsin and studied by MALDI-TOF MS. SDS gels revealed the differences between ConA non-bound and bound fractions. The majority of proteins were found in non-bound fractions. Several important glycoproteins were confirmed in studied materials: barley grain (serine carboxypeptidase; alpha-amylase inhibitor BMAI-1), barley malt (e.g., β-d-xylosidase) and Arabidopsis (β-d-xylosidase, peroxidase, etc.).