Dual-function protein in plant defence: seed lectin from Dolichos biflorus (horse gram) exhibits lipoxygenase activity.
Plant-pathogen interactions play a vital role in developing resistance to pests. Dolichos biflorus (horse gram), a leguminous pulse crop of the subtropics, exhibits amazing defence against attack by pests/pathogens. Investigations to locate the possible source of the indomitable pest resistance of D. biflorus, which is the richest source of LOX (lipoxygenase) activity, have led to a molecule that exhibits LOX-like functions. The LOX-like activity associated with the molecule, identified by its structure and stability to be a tetrameric lectin, was found to be unusual. The evidence for the lectin protein with LOX activity has come from (i) MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS, (ii) N-terminal sequencing, (iii) partial sequencing of the tryptic fragments of the protein, (iv) amino acid composition, and (v) the presence of an Mn2+ ion. A hydrophobic binding site of the tetrameric lectin, along with the presence of an Mn2+ ion, accounts for the observed LOX like activity. This is the first ever report of a protein exhibiting both haemagglutination and LOX-like activity. The two activities are associated with separate loci on the same protein. LOX activity associated with this molecule adds a new dimension to our understanding of lectin functions. This observation has wide implications for the understanding of plant defence mechanisms against pests and the cellular complexity in plant-pathogen interactions that may lead to the design of transgenics with potential to impart pest resistance to other crops.
Roopashree
Subbaiah
S
Department of Protein Chemistry and Technology, Central Food Technological Research Institute, Mysore 570020, India.
Singh
Sridevi Annapurna
SA
Gowda
Lalitha R
LR
Rao
A G Appu
AG
D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology; D031294:Dolichos / Q000187:drug effects / Q000201:enzymology*; D004795:Enzyme Stability; D008084:Lipoxygenase / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008969:Molecular Sequence Data; D037121:Plant Lectins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000201:enzymology*; D016415:Sequence Alignment; D013057:Spectrum Analysis; D013379:Substrate Specificity; D013696:Temperature
D000906:Antibodies; D016859:Lipoxygenase Inhibitors; D037121:Plant Lectins; D008084:Lipoxygenase