Characterization of the yam tuber storage proteins from Dioscorea batatas exhibiting unique lectin activities

Mariam Gaidamashvili, Yuki Ohizumi, Shinichiro Iijima, Tomo Takayama, Tomohisa Ogawa, Koji Muramoto

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)

Abstract

Four major proteins designated DB1, DB2, DB3, and DB4 were isolated and characterized from the yam tuber Dioscorea batatas. The ratios of their yields were 20:50:20:10. DB1 was a mannose-binding lectin (20 kDa) consisting of 10-kDa subunits and was classified as the monocot mannose-binding lectin family. DB2, accounting for 50% of the total protein, was the storage protein, commonly called dioscorins consisting of a 31-kDa subunit. On the basis of amino acid sequence, DB2 was classified to be dioscorin A. DB3 was a maltose-binding lectin, having an apparent molecular mass of 120 kDa and composed of a 66-kDa subunit and two 31-kDa subunits (DB3S). The 66-kDa subunit was further composed of two 31-kDa subunits (DB3L) cross-linked by disulfide bonds. DB3L and DB3S (242 and 241 amino acid residues, respectively) were homologous with each other with 72% sequence identity. They showed a sequence homology to dioscorin B and dioscorin A from Dioscorea alata, with 90 and 93% identity, respectively, and to carbonic anhydrase from Arabidopsis thaliana with about 45% identity. DB3S had one intrachain disulfide bond located at Cys28-Cys187, whereas DB3L had one interchain disulfide bond (Cys40-Cys 40′) in addition to the intrachain disulfide bond (Cys 28-Cys188) to form a 66-kDa subunit. DB1 and DB3 agglutinated rabbit erythrocytes at 2.7 and 3.9 μg/ml, respectively. Despite the structural homology between DB2 and DB3, DB2 had no lectin activity. The 66-kDa subunit itself revealed the full hemagglutinating activity of DB3, indicating that DB3L but not DB3S was responsible for the activity. The hemagglutinating activity of DB3 required Ca2+ ions and was exclusively inhibited by maltose and oligomaltoses (e.g. maltopentaose and maltohexaose) but not by D-glucose. DB3 could not be classified into any known plant lectin family. DB4 was a chitinase, homologous to an acidic chitinase from Dioscorea japonica. DB1, DB2, and DB3 did not show any activity of carbonic anhydrase, amylase, or trypsin inhibitor activity. These results show that two of the four major proteins isolated from the yam tubers D. batatas have unique lectin activities.

Original languageEnglish
Pages (from-to)26028-26035
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number25
DOIs
Publication statusPublished - 2004 Jun 18

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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