Abstract: An isolated RBP with at least one of the following characteristics: a) a molecular weight of approximately 65-70 kDa and more preferably 66-69 kDa; b) a pI of greater than 10 or less than 3; c) a dissociation constant of approximately 1.5×10?6 when bound to the rhamnose moiety of solamargine; d) adapted to bind to a rhamnose affinity column prepared according to example 1 and under the conditions set out therein; e) adapted to be eluted from the column in example 1 with a 100 mM rhamnose solution; f) insoluble in aqueous solution; and g) soluble in highly denaturing buffers containing greater that approximately 2% surfactant.