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.
Keywords: trichisanthes kirilowii lectin, ribosome-inactivating proteins rips, type 2 ribosome-inaactivating proteins rips, tri, trichosanthin, momordica charantia, bryonia dioica, bryodin, mmomorcharin, krl-1
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