Ribosome-inactivating proteins from plant cells in culture

• Published in: Biochemical journal Vol. 257; no. 3; pp. 801 - 807
• Main Authors: Barbieri, L, Bolognesi, A, Cenini, P, Falasca, A.I, Minghetti, A, Garofano, L, Guicciardi, A, Lappi, D, Miller, S.P, Stirpe, F
• Format: Journal Article
• Language: English
• Published: England 01.02.1989
• Subjects: Amino Acid Sequence; Animals; cell culture; Cell-Free System; Cells, Cultured; inactivation; Molecular Sequence Data; Phytolacca americana; Plant Extracts; plant proteins; Plant Proteins - metabolism; protein synthesis; Rabbits; Ribosomal Proteins - antagonists & inhibitors; ribosome-inactivating protein; ribosomes; Ribosomes - metabolism; RNA, Ribosomal; Saponaria officinalis; Zea mays
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2570801

1. Ribosome-inactivating proteins were found in high amounts in one line of cells of Phytolacca americana (pokeweed) cultured in vitro and, in less quantity, in lines of Saponaria officinalis (soapwort) and of Zea mays (corn) cells. 2. The main ribosome-inactivating protein from pokeweed cells was purified to homogeneity. It is a protein with Mr 29,000 and basic pI, similar to the 'pokeweed antiviral protein' (PAP), a ribosome-inactivating protein from pokeweed leaves. We propose to call the pokeweed antiviral protein isolated from pokeweed cells PAP-C. 3. PAP-C inactivates ribosomes in a less-than-equimolar ratio, thus inhibiting protein synthesis by a rabbit reticulocyte lysate with an IC50 (concentration causing 50% inhibition) of 0.067 nM (2 ng/ml), and modifies rRNA in a manner apparently identical to that of ricin and other ribosome-inactivating proteins. It inhibits protein synthesis by intact cells with an IC50 of 0.7-3.4 microM, and is toxic to mice with an LD50 of 0.95 mg/kg.