Question

What proteins might be most likely to co-purify with Con A during affinity chromatography on Sephadex?

Answer 1

There might be 2 aspects in the question.

Concanavalin A (Con A) is a lectin isolated from the jack bean. At pH >7 it exists as a tetramer. This is the species most likely attached to the resin. Con A is not a glycoprotein. It does not contain cysteine residues. Unlike most other lectins, Con A is a metalloprotein and requires a transition metal ion, such as manganese and calcium ions for binding. Each subunit of Con A binds one calcium ion and one manganese ion. Removal of these cations under acidic conditions abolishes the carbohydrate-binding activity. Con A binds specifically to mannosyl and glucosyl residues of polysaccharides and glycoproteins. Unmodified hydroxyl groups at the C3, C4, and C6 positions of D-glucopyranosyl or D-mannopyranosyl rings may be essential for binding. General adsorption and desorption procedures and methods to prevent leakage of the lectin from the matrix have been described.This product has been used to isolate human fibroblast interferon10 and glycoprotein from sarcoplasmic reticulum. Con A Sepharose has been used with SDS (0.05%) and Triton X-100.

Concanavalin A bound to Sepharose has been used for the purification of brain β-galactosidase, α-L-fucosidase, α-D-mannosidase, arylsulphatase and β-glucuronidase.  lysosomal acid α-mannosidase and a cytosolic neutral mannosidase were separable by concanavalin A-Sepharose chromatography. Similarly lysosomal and microsomal β-glucuronidases were separable using gradient elution with α-methyl glucoside.

So, we see that the above mentioned protein may co-purify using Con A Sepharose affinity chromatography.

But if we consider Co-purify with Con A, that situation only arise while we are isolating Concanavalin A from  the seeds of Jackbean (Canavalia ensiformis). This process requires affinity chromatography with  maltamly sepharose beads or by calcium alginate cellulose bead with transitional metal.

In those situation canavalin, another protein from jack beans with plant albumin might co-purify with con A. (experimented by  D. BREESE JONES AND CARL O. JOHNS, the Bureau of Ch.emistry, United States Department of Agriculture, Washington.)

Thanks for asking.