Lectins jack bean

It is only within the past decade that lectins have been purified to a homogeneity demonstrable by physicochemical and immunological criteria. Although Sumner and Howell crystallized the jack-bean lectin (concanavalin A or con A) over forty years ago, they were unable to free it completely from carbohydrate contaminants.102... 

The simplest known sugar derivatives that interact with the jack-bean lectin are l,5-anhydro-2-deoxy-D-arahino-hexitol and 1,4-anhydro-D-arabinitol.168,215 These alditols contain the minimal structural features required for binding to con A, namely, unmodified hydroxyl groups of the B-arabino configuration at C-3, C-4, and C-5 of the... 

Scheme 5.11 DCL of disulfide

Concanavalin A is a plant lectin from the jack bean (Canavalia ensiformis) which binds with high affinity to mannose residues of glycoproteins. Concanavalin A is known to stimulate the tyrosine kinase activity of the INSR (3-subunit with consecutive activation of kinases downstream the insulin receptor (IRS, PI 3-kinase). It is believed that Concanavalin A stimulates the activation and autophosphorylation of the INSR kinase through aggregation of the receptor, although the precise mechanism of action is unclear. 

Like the jack-bean and pea lectins, the lentil agglutinin interacted with 2-0-(2-acetamido-2-deoxy-j8-D-glucopyranosyI)-D-mannose,210 providing evidence that the lentil lectin binds to internal 2-0-substituted D-mannopyranosyl residues that occur in animal glycoproteins. 

A comparative study of the hemagglutinating activities of the pea (Pisum sativum), the lentil (Lens culinaris), and the jack-bean (Canavalia ensiformis) lectins towards the erythrocytes of fourteen different species showed446 that the pea and lentil lectins were, in all instances, more active than con A. Of great interest was the finding that, among these three lectins, con A alone was completely inactive against human erythrocytes (blood group, unspecified).446... 

The plant lectin concanavalin A, a metalloprotein isolated from the jack bean, has also received considerable attention. (588-590,630,631) Using the stopped flow NMR technique three distinct conformation states of the protein, when it is bound to Mn, Ca, and a-methyl-D-mannoside, (630) have been deduced. 

Lectin from jack bean (Canavalia ensiformis)... 

The above lectins are from jack bean and wheat germ, respectively. Unfortunately, this nomenclature depends on experimental refinement. Just compare the name of the lectin from jack bean given here (Goldstein and Hayes 1978) with the one proposed in Section 15.5.3 (Liener et al. 1986). 

We will use the example of concanavalin A, abundant in jack bean flour. Final purification is done by absorption on a Sephadex column from which the lectin is eluted by a glucose solution. Concanavalin A is formed from four subunits— MW = 26 500 daltons—associated in dimers below pH 5.6 and tetramers above. Each subunit contains Mn, Ca, and a sugar binding site. Figure 15.2 shows their mode of association, with the location of the ions and the binding site. A very important part of polypeptide chains are j8-sheets. These are the regions where the associations between monomers take place. 

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