A novel ribosome-inactivating protein, designated Trichosanthrip, was purified from mature seeds of Trichosanthes kirilowii Maxim by cation-exchange and gel-filtration chromatography. Trichosanthrip migrated as a single band in SDS-PAGE, with an apparent molecular mass of similar to 13 kDa. The molecular mass of Trichosanthrip was 10,964.617 Da as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Trichosanthrip showed N-glycosidase activity on 28 S rRNA and strongly inhibited cell-free protein synthesis, with an IC50 of 1.6 ng/ml. Liquid chromatography-tandem mass spectrometry showed that Trichosanthrip was a novel protein with similar sequence to other proteins present in members of the Cucurbitaceae. (C) 2009 Published by Elsevier Inc.