S-type lectins

One of two classes of lectin produced by animal cells. The classification of animal lectins into two classes, the other being the C-type, was originally proposed by K. Drickamer. The carbohydrate binding activity of the S-type lectins requires their cysteines to have free thiols and does not need divalent cations (cf. C-type lectins). They mostly have molecular masses in the range 14-16 kD and often form dimers and higher oligomers. The carbohydrate recognition domain contains a number of critically conserved amino acids and largely binds to b -galactosides. S-type lectins certainly occur as cytoplasmic proteins but the existence of extracellular S-type lectins is still a matter of debate.