Model Number

HG 40004 Con A

Con A, ConA Sepharose 4B, ConA Sepharos CL 6B

ConA from jack bean was the first lectin whose structure became known. The protein consists of 237 amino acids (Mr 26500) and has two metal binding sites. Structural features of the amino acid chain are two antiparallel beta sheets. One of these is built from seven strands. The other sheet contains six strands. There are only minor helical sections. In its native state one molecule of ConA binds two metal atoms: one Ca2+ and one ion of a transition metal, usually Mn2+. The metal atoms are bound by amino acids in a loop that points away from the seven-strand pleated sheet, Ligands for the transition metal are Glu8, Asp10, Asp19 und His24, the calcium ion is bound by Asp10, Tyr12, Asn14 und Asp19  .

The binding site for the sugar is adjacent to the metal atoms (in this example a trisaccharide formed from mannose is bound). Nitrogen atoms from Asn14, Leu99, Tyr100, Asp208 und Arg228 are involved in fixing the saccharide.

In its active state ConA forms aggregates. Joining two six stranded sheets to an extended twelve stranded one results in a dimeric molecule. Two dimers form a functional complex by layering side to side the twelve stranded sheets. The resulting complex now contains four spatially well separated binding sites for oligosaccharides. Threreby it is well apt for building destructively aggregates of e. g. erythrocytes.