About the Lectin
Rhizomes of the stinging nettle contain a lectin with some unusual biochemical and molecular properties. Urtica dioica is a generally weak hemagglutinin, regardless of blood type. The lectin is not inhibited by simple sugars, but it is inhibited by oligomers of β(1,4)-linked GlcNAc 1 . Purified UDA is the smallest plant lectin isolated, with a molecular weight between 8-9,000 Da. Various analytical techniques have been used to show that UDA is composed of only a single polypeptide chain. This is in contrast to virtually all other lectins, which are composed of at least two subunits. UDA is extraordinarily stable; it retains its activity even when subjected to acid conditions of pH 1.0, or when heated to 80°C for up to fifteen minutes. UDA contains two chitin-binding hevein domains 2 of non-identical affinities for chito-oligosaccharides, as demonstrated by equilibrium dialysis 3 , UV difference spectroscopy 3 , and NMR studies 4 . It therefore is homologous with other GlcNAc-binding lectins, such as WGA 5 , as well as chitinases. Pure UDA is an inducer of interferon production from human lymphocytes. Its interferon production activity is lower than that of Con A, and its activity is concentration dependent. It is a specific “superantigen”-type activator of the Vβ8.3 class of T-cells 6 , leading to their rapid proliferation, followed by depletion from a T-cell population 7 . UDA also exhibits potent and selective inhibition of human immunodeficiency and cytomegalovirus replication in vitro, similar to mannose-specific lectins such as GNA 8 . Several other chitin binding lectins (including WGA, STA, and DSA) have been thought to exhibit antifungal properties. Recent studies have shown that this activity has been due to contaminating chitinases. In contrast, UDA has been shown to possess strong antifungal activity, with no contaminating chitinase activity 9,10 , although its gene also contains an active chitinase 11 . In contrast to other reports 9 , rabbit anti-WGA supplied by EY Laboratories does cross react with purified UDA.
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|Buffer||0.01M Phosphate – 0.15M NaCl, pH 7.2-7.4.|
|Blood Group||Non-specific. O > A1 > A2.|
|Activity||Less than 65 μg/ml will agglutinate human type A1 and O erythrocytes. Less than 15 μg/ml will agglutinate neuraminidase treated cells.|
|Inhibitory Carbohydrate||Oligomers of β(1,4)-linked N‑acetyl‑D‑glucosamine.|
|Molecular Weight||A single polypeptide of 8-9,000 Da by SDS-PAGE. Gel filtration may yield a lower molecular weight due to interactions with the gel matrix.|