title: Structural analysis and binding properties of isoforms of tarin, the GNA-related lectin from Colocasia esculenta.
abstract: The lectins, a class of proteins that occur widely in animals, plants, fungi, lichens and microorganisms, are known for their ability to specifically bind to carbohydrates. Plant lectins can be classified into 12 families including the Galanthus nivalis agglutinin (GNA)-related lectin superfamily, which is widespread among monocotyledonous plants and binds specifically to mannose, a behavior that confers remarkable anti-tumor, anti-viral and insecticidal properties on these proteins. The present study characterized a mitogenic lectin from this family, called tarin, which was purified from the crude extract from taro (Colocasia esculenta). The results showed that tarin is a glycoprotein with 2-3% carbohydrate content, composed of least 10 isoforms with pIs ranging from 5.5 to 9.5. The intact protein is a heterotetramer of 47kDa composed of two non-identical and non-covalently associated polypeptides, with small subunits of 11.9kDa and large subunits of 12.6kDa. The tarin structure is stable and recovers or maintains its functional structure following treatments at different temperatures and pH. Tarin showed a complex carbohydrate specificity, binding with high affinity to high-mannose and complex N-glycans. Many of these ligands can be found in viruses, tumor cells and insects, as well as in hematopoietic progenitor cells. Chemical modifications confirmed that both conserved and non-conserved amino acids participate in this interaction. This study determined the structural and ligand binding characteristics of a GNA-related lectin that can be exploited for several different purposes, particularly as a proliferative therapeutic molecule that is able to enhance the immunological response.
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-909, Brazil. Electronic address: biopatbr@gmail.com.
authors.forename: Patrícia R
authors.initials: PR
authors.lastname: Pereira
authors.affiliation: Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: harwin@umich.edu.
authors.forename: Harry C
authors.initials: HC
authors.lastname: Winter
authors.affiliation: Instituto de Biologia, Universidade Federal Fluminense, Rio de Janeiro 4020141, Brazil. Electronic address: vericimo@vm.uff.br.
authors.forename: Mauricio A
authors.initials: MA
authors.lastname: Verícimo
authors.affiliation: Center for Structural Biology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: jmeagher@umich.edu.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Meagher
authors.affiliation: Center for Structural Biology, Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: jass@umich.edu.
authors.forename: Jeanne A
authors.initials: JA
authors.lastname: Stuckey
authors.affiliation: Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: igoldste@umich.edu.
authors.forename: Irwin J
authors.initials: IJ
authors.lastname: Goldstein
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-909, Brazil. Electronic address: paschv@iq.ufrj.br.
authors.forename: Vânia M F
authors.initials: VM
authors.lastname: Paschoalin
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-909, Brazil. Electronic address: joab@iq.ufrj.br.
authors.forename: Joab T
authors.initials: JT
authors.lastname: Silva
mesh_terms: D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D031060:Colocasia / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005916:Globulins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D037241:Mannose-Binding Lectins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D037121:Plant Lectins / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D035281:Plant Tubers / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D055550:Protein Stability; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
chemical_list: D005916:Globulins; D037241:Mannose-Binding Lectins; D037121:Plant Lectins; D010940:Plant Proteins; D011134:Polysaccharides; D020033:Protein Isoforms; C094238:TAR1 protein, Colocasia esculenta; C063117:snowdrop lectin; D014364:Tryptophan; D003545:Cysteine
keywords: Carbohydrate binding; Colocasia esculenta; Glycan microarray; Protein stability; Subunit isoform; Tarin