Quinqueginsin, a novel protein with anti-human immunodeficiency virus, antifungal, ribonuclease and cell-free translation-inhibitory activities from American ginseng roots.

A homodimeric protein designated quinqueginsin, with a molecular weight of 53 kDa, has been isolated from the roots of American ginseng Panax quinquefolium. It was unadsorbed on DEAE cellulose in low ionic strength and neutral pH, and adsorbed on Affigel blue gel and SP-Sepharose under similar conditions. Its N-terminal sequence bore similarity to those of plant ribosome inactivating proteins and fungal ribonucleases. The protein displayed a variety of biological activities. It possessed ribonucleolytic activity toward yeast tRNA and specific activity toward poly C. It inhibited cell-free translation in a rabbit reticulocyte lysate system with an IC(50) of 0.26 nM, and exerted antifungal action against Fusarium oxysporum, Rhizoctonia solani, and Coprinus comatus. An inhibitory action was expressed toward human immunodeficiency virus-1 reverse transcriptase. This action was potentiated after chemical modification with succinic anhydride.