Crystal structure of the peanut lectin - T-antigen complex. Carbohydrate specificity generated by water bridges

Abstract

Peanut lectin binds with high specificity to the tumour­ associated disaccharide GaI.81-3GaINAc, generally known as T-antigen. The crystal structure of the complex of the lectin with the disaccharide has been determined at 2.5 A resolution. Comparison of the structure with that of the corresponding complex with lactose reveals that the specificity of the lectin for T-antigen is generated primarily by two specific water­ mediated interactions, probably the first instance where water-bridges have been demonstrated to be responsi­ ble for generating specificity in protein-carbohydrate interactions. The elucidation of the structure of peanut lectin- T -antigen complex also provides a framework for exploring peanut lectin-based prognosis and diag­ nosis of certain types of carcinoma.