title: Structure predictions of two Bauhinia variegata lectins reveal patterns of C-terminal properties in single chain legume lectins.
abstract: 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.
authors.affiliation: Centro de Desenvolvimento Tecnológico, Núcleo de Biotecnologia, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: Gustavo M S G
authors.initials: GM
authors.lastname: Moreira
authors.forename: Fabricio R
authors.initials: FR
authors.lastname: Conceição
authors.forename: Alan J A
authors.initials: AJ
authors.lastname: McBride
authors.forename: Luciano da S
authors.initials: Lda S
authors.lastname: Pinto
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D036481:Bauhinia / Q000737:chemistry*; D006031:Glycosylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D037121:Plant Lectins / Q000737:chemistry* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D012639:Seeds / Q000737:chemistry*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D037121:Plant Lectins; D020033:Protein Isoforms