| Popis: |
Lectins are carbohydrate-binding and cell-agglutinating proteins of nonimmune origin. Lectins are used to isolate glycoproteins and follow alterations in glyco-part of glycoconjugates in pathological conditions such as cancer. In this study we isolated and characterized proteins from bovine and goat serum that sugar-specifically bound to jackfruit seed agglutinin (Jacalin). Jacalin is an α-galactose-specific lectin from the seeds of jackfruit (Artocarpus heterophyllus). Jacalin coupled to Sepharose (Jacalin-Sepharose) was packed to a volume of 0.5 ml in a Pasteur pipette. Serum (3 ml) was loaded on to the column and washed with phosphate buffered saline (PBS), pH 6.5 containing 0.15 M NaCl, (PBS 6.5) and bound proteins eluted with 0.15 M D-galactose in PBS 6.5. Isolated proteins were separated by SDS-PAGE and bands cut out and proteins identified by mass spectrometry. Six protein bands were visualized when the proteins isolated from bovine serum were subjected to SDS-PAGE. Out of these, four major bands were identified by mass spectrometry, and they were found to be inter-alpha-trypsin inhibitor heavy chain H4 precursor (104.7 kDa), factor XIIa inhibitor precursor (79.43 kDa), alpha-2-HS-glycoprotein precursor (Fetuin-A) (66.07 kDa) and apolipoprotein A-I precursor (Apo-AI) (28 kDa). From goat serum by affinity chromatography on Jacalin-Sepharose column, we obtained seven protein bands (125.89, 117.49, 104.71, 97.72, 83.18, 66.07 and 27 kDa). Some of these bands (117.49, 104.71, 66.07 and 27 kDa) are having the similar molecular weight counterparts in bovine serum. It is intriguing that one of the proteins identified (Apo-A1) is a non-glycosylated protein. Apo-A1 is a protein component of high-density lipoprotein (HDL). Since direct recognition of Apo-A1 by Jacalin has been ruled out, it is possible that glycoconjugates associated with Apo-A1 may mediate its binding to the lectin. Such glycoconjugates reported in the literature include lipopolysaccharides and transferrin. Further investigations on this phenomenon are ongoing. |
