Mutation of Asn128 to Asp of Phaseolus vulgaris leucoagglutinin (PHA-L) eliminates carbohydrate-binding and biological activity

Phytohaemagglutinin (PHA) is the major lectin present in theseeds of the common bean, Phaseolus vulgaris, and PHA-L is theleucocyte-agglutinating form of this lectin. This tetramericglycoprotein accumulates in the vacuoles of storage parenchymacells. Based on amino acid sequence comparisons of legume lectinsand the three-dimensional structure of lectin-carbohydrate complexes,Asn¹²⁸ can be identified as a likely candidate for site-directedmutagenesis to create a mutant PHA-L that does not bind carbohydrate.PHA-L N¹²⁸