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Ricin A chain can transport unfolded dihydrofolate reductase into the cytosol
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UNSPECIFIED (1997) Ricin A chain can transport unfolded dihydrofolate reductase into the cytosol. JOURNAL OF BIOLOGICAL CHEMISTRY, 272 (35). pp. 22097-22102. ISSN 0021-9258
Full text not available from this repository.Abstract
Ricin is a heterodimeric protein toxin. The ricin A chain is able to cross the membrane of intracellular compartments to reach the cytosol where it catalytically inactivates protein synthesis. It is linked via a disulfide bond to the B chain, a galactose-specific lectin, which allows ricin binding at the cell surface and endocytosis, To examine the potential of ricin A to carry proteins into the cytosol and the requirement for unfolding of the passenger protein, we connected mouse dihydrofolate reductase (DHFR) to ricin A by gene fusion via a spacer peptide, DHFR-ricin A expressed in Escherichia coli displayed the biological activities of the parent proteins and associated quantitatively with ricin B to form DHFR-ricin, The resulting toxin was highly cytotoxic to cells (4-8-fold less than recombinant ricin), DHFR-ricin cytotoxicity was inhibited by methotrexate, a DHFR inhibitor stabilizing DHFR-ricin A in a folded conformation, The DHFR moiety of DHFR ricin bound to the plasma membrane. Although methotrexate prevented this binding, it did not significantly affect DHFR-ricin endocytosis, which proceeded via ricin B chain. Intoxication kinetics data and a cell-free translocation assay demonstrated that protection of cells from DHFR-ricin cytotoxicity resulted from a selective inhibition by methotrexate of DHFR-ricin A translocation. We conclude that ricin A is a potential carrier of proteins to the cytosol, provided that the passenger protein is able to unfold for transmembrane transport.
| Item Type: | Journal Article |
|---|---|
| Subjects: | Q Science > QD Chemistry |
| Journal or Publication Title: | JOURNAL OF BIOLOGICAL CHEMISTRY |
| Publisher: | AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC |
| ISSN: | 0021-9258 |
| Date: | 29 August 1997 |
| Volume: | 272 |
| Number: | 35 |
| Number of Pages: | 6 |
| Page Range: | pp. 22097-22102 |
| Publication Status: | Published |
| URI: | http://wrap.warwick.ac.uk/id/eprint/16455 |
Data sourced from Thomson Reuters' Web of Knowledge
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