Purification and characterization of Luffin P1, a ribosome-inactivating peptide from the seeds of Luffa cylindrica.

A peptide designated Luffin P1 was purified from the seeds of Luffa cylindrica. Its molecular mass was determined to be 5226.1 Da by MALDI-TOF MS analysis. The purified Luffin P1 shows a strong inhibitory activity on protein synthesis in the cell-free rabbit reticulocyte lysate with IC(50) of 0.88 nM. Its reaction mechanism is the same as that of the ribosome-inactivating protein trichosanthin, which is an rRNA N-glycosidase. Besides, the results of gel filtration chromatography suggested the existence of polymers of Luffin P1 and polymerization of Luffin P1 enhanced its rRNA N-glycosidase activity. Luffin P1 was the smallest peptide yet reported that has translational inhibitory activity. The cDNA and deduced amino acid sequence of Luffin P1 has also been determined.