title: Comprehensive analysis of α 2-3-linked sialic acid specific Maackia amurensis leukagglutinin reveals differentially occupied N-glycans and C-terminal processing.
abstract: Seeds of Maackia amurensis constitutes two sialic acid specific agglutinins known as leukagglutinin and hemagglutinin. Maackia amurensis leukagglutinin (MAL) recognizes α2-3-linked sialic acid present mainly in N-glycans and composed of two disulfide linked monomers. It exhibits potential N-glycosylation sites (four PNGs) which have been assumed to undergo differential occupancy. In this study we have characterized the site specific macro- and microheterogeneity of monomers in detail by analysing N-glycopeptides and peptides through liquid chromatography coupled to ion trap mass spectrometer in MS3mode (LC-MSn). We observed the presence of mainly paucimannose N-glycans at Asn61, Asn113and Asn191whereas a high mannose type with varying Man5-9occurs at Asn179. Interestingly Asn179and Asn191exhibited differential occupancy which was evident by the presence of non-glycosylated peptides. This has contributed to the difference in molecular mass of monomers upon SDS-PAGE. Further the presence of disulfide linked peptides confirmed the covalent linkage of monomers which also undergoes uniform C-terminal processing.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India.
authors.forename: Gnanesh Kumar
authors.initials: GK
authors.lastname: B S
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India. Electronic address: surolia@mbu.iisc.ernet.in.
authors.forename: Avadhesha
authors.initials: A
authors.lastname: Surolia
mesh_terms: D000595:Amino Acid Sequence; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006031:Glycosylation; D029901:Maackia / Q000737:chemistry*; D010835:Phytohemagglutinins / Q000737:chemistry*; D011499:Protein Processing, Post-Translational; D020539:Sequence Analysis, Protein; D012794:Sialic Acids / Q000737:chemistry*
chemical_list: D010835:Phytohemagglutinins; D012794:Sialic Acids
keywords: C-terminal processing; Legume lectin; Macroheterogeneity