<Emphasis Type="Italic">Myo</Emphasis>-inositol Binding Site of Concanavalin A

CONCANAVALIN a agglutinates erythrocytes from various animal species, yeast cells, starch granules and some bacteria¹ and it complexes with many other substances which contain specific saccharides^2–5. When bound to saccharides of cell surfaces, concanavalin A will return tissue cultures of transformed fibroblasts to normal growth rates⁶ and inhibit growth of various tumours in vivo.^7,8 The protein equivalent weight per saccharide, transition metal ion and Ca²⁺ ion binding sites has been shown by equilibrium dialysis to be about 30.000^3,9. Transition metal and Ca²⁺ ions are both required for the saccharide binding⁹. The crystallographic asymmetric unit contains a subunit of 27,000 daltons^10–12. Four subunits, which are identical, interact through a point of 222 symmetry to form a “pseudotetrahedral” molecule of about 108,000 daltons¹⁰. Moreover, the pair of subunits related around the x-axis are more firmly associated than the other two pairs¹⁰.