The Disulfide Bond Connecting the Chains of Ricin

Studies on the disulfide bond connecting the two polypeptide chains of ricin are reported. Reduction of this bond in the native protein requires approximately 50-fold more mercaptoethanol than the reduction of the bond in the protein denatured by sodium dodecyl sulfate. An improved procedure for the...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1978-03, Vol.75 (3), p.1096-1100
Main Authors: Lappi, Douglas A., Kapmeyer, Wolfgang, Beglau, Janice M., Kaplan, Nathan O.
Format: Article
Language:English
Subjects:
Biochemistry
Chemical bonding
Cultured cells
Disulfides
HeLa cells
HeLa Cells - drug effects
Lethal Dose 50
Macromolecular Substances
Phosphates
Protein Biosynthesis
Protein Conformation
Protein synthesis
Ricin - isolation & purification
Ricin - pharmacology
Ricin - toxicity
Sodium
Structure-Activity Relationship
Sulfates
Toxicity
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Summary:Studies on the disulfide bond connecting the two polypeptide chains of ricin are reported. Reduction of this bond in the native protein requires approximately 50-fold more mercaptoethanol than the reduction of the bond in the protein denatured by sodium dodecyl sulfate. An improved procedure for the formation of this disulfide bond from recombined chains is reported. A and B chains spontaneously and rapidly reassociate into a stable complex with a sedimentation velocity similar to that of native oxidized ricin before the disulfide bond reforms. The mixture of both chains also behaves on Bio-Gel P-100 like native oxidized ricin. However, the complex formed by the two chains, assayed before the disulfide bond can reform, and reduced ricin, carboxymethylated to prevent reoxidation, shows a significant decrease in toxicity to mice and a decrease in ability to inhibit protein synthesis in HeLa cells in culture.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.75.3.1096