Concanavalin A

Literature References: The most extensively investigated member of the lectin family of plant proteins. Unlike most lectins, it lacks covalently bound carbohydrate and therefore is not a glycoprotein. Isolated from jack bean, Canavalia ensiformis, Papilionatae: J. B. Sumner, S. F. Howell, J. Bacteriol. 32, 227 (1936). Its function in C. ensiformis is unknown, but it agglutinates a variety of somatic and germ line cells through specific interaction with saccharide-containing cell surface receptors and restores the growth pattern of virus-transformed fibroblasts in tissue culture to that of normal cells, cf. M. M. Burger, K. D. Noonan, Nature 228, 512 (1970); G. M. Edelman, C. F. Millette, Proc. Natl. Acad. Sci. USA 68, 2436 (1971). Differential toxicity on normal and transformed cells in vitro and inhibition of tumor development in vivo have also been reported: J. Shoham et al., Nature 227, 1244 (1970). The molecule consists of identical polypeptide subunits of mol wt about 27,000, existing as dimers in soln at pH <6 and as tetramers at physiologic pH. The proposed amino acid sequence contains 238 residues; con A has also been shown to have binding site for transition metal ions and calcium ions in addition to saccharide binding sites: G. M. Edelman et al., Proc. Natl. Acad. Sci. USA 69, 2580 (1972). The transition ion, usually Mn+2 or Ca+2, apparently stabilizes the formation of the specific saccharide binding site: M. Shoham et al., Biochemistry 12, 1914 (1973). Circular dichroism-NMR study of metal binding sites: A. R. Palmer et al., ibid. 19, 5063 (1980). Oligosaccharide binding study: A. Vanlands et al., Eur. J. Biochem. 103, 307 (1980). Use of con A to study immunoregulation of human T cells: D. M. Dwyer, C. Johnson, Clin. Exp. Immunol. 46, 237 (1981); E. L. Larson et al., Immunobiology 161, 5 (1982). For general refs, see Lectins.