Proteins with abortifacient, ribosome inactivating, immunomodulatory, antitumor and anti-AIDS activities from Cucurbitaceae plants.

1. The biochemical characteristics and biological activities of eight Cucurbitaceae plant proteins designated trichosanthin (isolated from tubers of Trichosanthes kirilowii), beta-trichosanthin (isolated from tubers of Trichosanthes cucumeroides), alpha- and beta-momorcharins (isolated from seeds of Momordica charantia), momorchochin (isolated from tubers of Momordica cochinchinensis), luffaculin (isolated from seeds of Luffa acutangula) and luffin-a and luffin-b (isolated from seeds of Luffa cylindrica), were reviewed. 2. The isolation procedures for all eight proteins are based on aqueous extraction, acetone fractionation and ion exchange chromatography. Ammonium sulfate precipitation and gel filtration are steps which may be included to improve purification. 3. The proteins are basic in nature and possess a molecular weight of approx. 30,000. All except trichosanthin are glycoproteins. The content of Asx and Glx residues is high. The N-terminal amino acid residue is Asp. Their amino acid compositions and N-terminal amino acid sequences are similar. 4. Circular dichroism spectroscopic studies revealed that trichosanthin, alpha- and beta-momorcharins possess similar secondary but different tertiary structures. 5. Most of the proteins are immunologically distinct. 6. The proteins exhibit abortifacient, antitumor, ribosome inactivating and immunomodulatory activities. Trichosanthin manifests anti-human immunodeficiency virus activity.