Crystal Structure of Trichosanthes Kirilowii Lectin-1 and its Relation to the Type 2 Ribosome Inactivating Proteins

Crystal structure of a two-chain lectin, isolated from the tuber of Trichosanthes kirilowii, was solved by the molecular replacement method using abrin-a as probe. From the present density map at 2.7A resolution, it could be seen that a residue corresponding to an invariant tyrosine locating in the active site of ribosome-inactivating proteins (RIPs) is replaced with a non-aromatic one. This may be the reason why this kind of lectins has no RIPs activity, even though they possess some properties similar to type 2 RIPs.