Probing genetic variation and glycoform distribution in lectins of the Erythrina genus by mass spectrometry

Structure predictions of two Bauhinia variegata lectins reveal patterns of C-terminal properties in single chain legume lectins

Bauhinia variegata lectins (BVL-I and BVL-II) are single chain lectins isolated from the plant Bauhinia variegata. Single chain lectins undergo post-translational processing on its N-terminal and C-terminal regions, which determines their physiological targeting, carbohydrate binding activity and pattern of quaternary association. These two lectins are isoforms, BVL-I being highly glycosylated, and thus far, it has not been possible to determine their structures. The present study used prediction and validation algorithms to elucidate the likely structures of BVL-I and -II. The program Bhageerath-H was chosen from among three different structure prediction programs due to its better overall reliability. In order to predict the C-terminal region cleavage sites, other lectins known to have this modification were analysed and three rules were created: (1) the first amino acid of the excised peptide is small or hydrophobic; (2) the cleavage occurs after an acid, polar, or hydrophobic residue, but not after a basic one; and (3) the cleavage spot is located 5-8 residues after a conserved Leu amino acid. These rules predicted that BVL-I and -II would have fifteen C-terminal residues cleaved, and this was confirmed experimentally by Edman degradation sequencing of BVL-I. Furthermore, the C-terminal analyses predicted that only BVL-II underwent α-helical folding in this region, similar to that seen in SBA and DBL. Conversely, BVL-I and -II contained four conserved regions of a GS-I association, providing evidence of a previously undescribed X4+unusual oligomerisation between the truncated BVL-I and the intact BVL-II. This is the first report on the structural analysis of lectins from Bauhinia spp. and therefore is important for the characterisation C-terminal cleavage and patterns of quaternary association of single chain lectins.

Mass spectrometric characterization of isoform variants of peanut (Arachis hypogaea) stem lectin (SL-I)

Matrix assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometric (MS) analysis of purified Arachis hypogaea stem lectin (SL-I) and its tryptic digests suggested it to be an isoformic glucose/mannose binding lectin. Two-dimensional gel electrophoresis of SL-I indicated six isoforms (A1-A6), which were confirmed by Western blotting and MALDI-TOF MS analysis. Comparative analysis of peptide mass spectra of the isoforms matched with A. hypogaea lectins with three different accession numbers (Q43376_ARAHY, Q43377_ARAHY, Q70DJ5_ARAHY). Tandem mass spectrometric (MS/MS) analysis of tryptic peptides revealed these to be isoformic variants with altered amino acid sequences. Among the peptides, the peptide T12 showed major variation. The (199)Val-Ser-Tyr-Asn(202) sequence in peptide T12 of A1 and A2 was replaced by (199)Leu-Ser-His-Glu(202) in A3 and A4 (T12') while in A5 and A6 this sequence was (199)Val-Ser-Tyr-Val(202) (T12''). Peptide T1 showed the presence of (10)Asn in the isoforms A1-A5 while in A6 this amino acid was replaced by (10)Lys (T1'). Overall amino acid sequence as identified by MS/MS showed a high degree of similarity between A1, A2 and among A3, A4, A5. Carbohydrate binding domain and adenine binding site seem to be conserved.

Glycosylation analysis of glycoproteins and proteoglycans using capillary electrophoresis-mass spectrometry strategies

This review highlights recent developments in glycosylation analysis by modern MS in combination with CE based preseparation. Focused on CE-MS strategies aimed for glycotyping, the review addresses the detailed glycoform analysis of glycoproteins, glycopeptides, and proteoglycans. Glycoform analysis in the context of modern glycoproteomics is briefly addressed, as well. CZE, CIEF, and frontal analysis CE approaches hyphenated to high-resolution multistage MS for the detailed analysis of protein-linked glycan structures are overviewed in a comprehensive way. Advantages and limitations of various methodological approaches and techniques as well as mass spectrometric instrumentation are discussed in the particular context of glycoanalysis.

Capillary electrophoresis - mass spectrometry: survey on developments and applications 2003-2004

The major developments and applications related to CE-MS over the last two years (2003-2004) and most of the reviews and applications found in the ISI Web of Science and publisher data bases are presented in a tabulated way. This article complements our previous review "Capillary electrophoresis - mass spectrometry: 15 years of developments and applications", Electrophoresis, 2003, 24, 3837-3867 for the last two years 2003-2004. All cited articles were analyzed in a way to illustrate (i) in which journals CE-MS-related papers were mostly found over the last decades and (ii) which commercial CE-, MS-instrumentations or CE-MS combinations were mostly used in the European, Asian, and American continent. Additionally, like it was done in our last review, the reader will rapidly find applications classified as forensics, environment, bioanalytics, pharmaceutics, and metabolites.

New features of site-specific horseradish peroxidase (HRP) glycosylation uncovered by nano-LC-MS with repeated ion-isolation/fragmentation cycles

Horseradish peroxidase (HRP) is widely used in biomedical research as a reporter enzyme in diagnostic assays. In addition, it is of considerable interest as a model glycoprotein with core-xylosylated and -(alpha1-3)-fucosylated N-glycans that form antigenic elements of plant allergens and parasitic helminths. Using a combination of techniques comprising (1) nano-liquid chromatography (LC)-mass spectrometry (MS)/MS with multiple selection/fragmentation cycles of HRP tryptic (glyco-)peptides, (2) nano-electrospray MS of intact HRP, and (3) carbohydrate linkage analysis, it was revealed that most of the HRP N-glycosylation sites can be occupied with an alternative Fuc(1-3)GlcNAc-disaccharide. Two main variants of HRP occur: The major population (approximately 60%) has eight glycosylation sites carrying core(1-3)fucosylated, xylosylated, trimannosyl N-glycans, with the ninth potential N-glycosylation site Asn316 not occupied. Another group of HRP carries seven of the above-mentioned N-glycans, with an eighth N-glycosylation site carrying the alternative Fuc(1-3)GlcNAc-unit (approximately 35%). In addition, minor subsets of HRP were found to contain a xylosylated, trimannosyl N-glycan lacking core-fucosylation as a ninth N-glycan attached to Asn316, which has hitherto been assumed to be unoccupied. The finding of these new features of glycosylation of an already exceptionally well-studied glycoprotein underscores the potential of the nano-LC-MS(n) based analytical approach followed.

Current literature in mass spectrometry

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (5 Weeks journals ‐ Search completed at 8th. Sept. 2004)