Characterization of ribosome-inactivating proteins isolated from Bryonia dioica and their utility as carcinoma-reactive immunoconjugates.

Abstract

Two ribosome-inactivating proteins (RIPs) were isolated and characterized from the roots of Bryonia dioica. One of these was a novel 27-kDa protein termed bryodin 2 (BD2), while the second was a previously reported RIP, referred to here as bryodin 1 (BD1). The amino-terminal sequence obtained for BD2 was similar, but distinct from BD1, ricin A chain, trichosanthin, and momorcharin. BD2-specific monoclonal antibodies were generated and found not to react with BD1 or ricin A chain. Purified BD1 and BD2 RIP inhibited protein synthesis in a cell-free in vitro translation assay at EC50 values of 7 and 9 pM, respectively. Intravenous administration of BD1 was less toxic to mice than BD2, with LD50 values of > 40 for BD1 and 10-12 mg/kg for BD2. Primary human endothelial cells were 5-8-fold less sensitive to BD1 and BD2 than compared to ricin A chain. BD1 and BD2 were constructed as immunoconjugates with the chimeric form of BR96 (chiBR96), a carcinoma-reactive, internalizing antibody. ChiBR96-BD1 and chiBR96-BD2 were found to bind to and kill BR96 antigen-positive carcinoma cells while not killing antigen-negative carcinoma cells. Bryodins represent RIPs that may be useful in constructing immunotoxin conjugates with reduced toxicity and vascular sensitivity, as compared to ricin A chain immunotoxins.

• Authors: C B Siegall, S L Gawlak, D Chace, E A Wolff, B Mixan, H Marquardt
• Journal: Bioconjugate chemistry (Bioconjug Chem) 1994 Sep-Oct Vol. 5 Issue 5 Pg. 423-9 ISSN: 1043-1802 [Print] United States
• PMID: 7849072 (Publication Type: Journal Article)

Chemical References

• Antibodies, Neoplasm
• Immunotoxins
• Plant Proteins
• Protein Synthesis Inhibitors
• Ribosome Inactivating Proteins, Type 1
• Toxins, Biological
• bryodin

Topics

• Amino Acid Sequence
• Animals
• Antibodies, Neoplasm (chemistry, immunology)
• Cell Death
• Endothelium, Vascular (cytology)
• Female
• Humans
• Immunotoxins (chemistry, immunology, toxicity)
• Lethal Dose 50
• Mice
• Mice, Inbred BALB C
• Molecular Sequence Data
• Plant Proteins (chemistry, immunology, isolation & purification, toxicity)
• Plants (chemistry)
• Protein Synthesis Inhibitors (pharmacology)
• Ribosome Inactivating Proteins, Type 1
• Ribosomes (drug effects)
• Toxins, Biological
• Tumor Cells, Cultured