The crystal structure of the sclerotium rolfsii lectin

Lectins are non-enzymic carbohydrate binding proteins present in plants, bacteria, fungi, and animals, which preferentially bind reversibly to specific carbohydrate structures whether free in solution or on cell surfaces and play important role in cell recognition. Sclerotium rolfsii, a soil borne plant pathogenic fungus capable of forming fruiting bodies referred to as sclerotial bodies, secretes a cell wall associated TF antigen (Galβ13GalNAc-α1Ser/Thr) specific lectin (SRL) [1, 2]. Recent findings indicate that SRL is expressed on the mycelia at the time of sclerotial body formation and facilitates the aggregation of the mycelium by interacting with its endogenous glycosyl ceramide receptor(s) having specific carbohydrate moiety [3]. SRL is a monomer under acidic conditions (pH 4.3) with a molecular weight of 17 kDa and forms a dimer at neutral or basic pH [1]. SRL displays a clear specificity for TF antigen [2], one of the most specific human tumourassociated structures [4]. Understanding the molecular basis of the specificity of SRL for the TF antigen may help in the elucidation of the recognition mechanism of tumour-associated glycoproteins by other lectins.