Transport of ricin A chain after prior treatment of mouse leukemia cells with ricin B chain.

Abstract

Ricin A chain acts to inhibit protein synthesis only if it penetrates the plasma membrane, and this requires the participation of the B chain. The two chains are held together in ricin by a single disulfide bond. In this paper, it is shown that the addition of A chain to mouse leukemia cells (AKR SL3) after the cells were first reacted with purified ricin B chain also results in efficient inhibition of protein synthesis. The data indicated that B chain bound to the cell surface was capable of causing the transport of A chain. The quantities of ricin and of B chain (in the presence of a saturating amount of A chain) required to inhibit protein synthesis by 50% are nearly identical, indicating that there is little difference in the toxicity to cultured cells between ricin and the A chain-B chain heterodimer formed from purified subunits. However, if the addition of A chain to B chain-treated cells was delayed sufficiently long (90 to 120 min), B chain was no longer able to cause A chain transport and the consequent inhibition of protein synthesis. Direct binding studies indicated that only a fraction of the bound 125I-B chain was internalized during this time. No proteolytic degradation of 125I-B chain could be detected after 3 h incubation with the cells.

• Authors: L L Houston
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 257 Issue 3 Pg. 1532-9 (Feb 10 1982) ISSN: 0021-9258 [Print] United States
• PMID: 7056731 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Macromolecular Substances
• Ricin

Topics

• Animals
• Biological Transport (drug effects)
• Cell Membrane (drug effects, metabolism, ultrastructure)
• Kinetics
• Leukemia, Experimental (metabolism)
• Macromolecular Substances
• Mice
• Microscopy, Electron
• Protein Biosynthesis
• Ricin (pharmacology)