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The N-terminal ricin propeptide influences the fate of ricin A-chain in tobacco protoplasts
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Jolliffe, Nicholas A., Di Cola, Alessandra, Marsden, Catherine J., Lord, Mike, Ceriotti, Aldo, Frigerio, Lorenzo and Roberts, L. M. (Lynne M.) (2006) The N-terminal ricin propeptide influences the fate of ricin A-chain in tobacco protoplasts. JOURNAL OF BIOLOGICAL CHEMISTRY, 281 (33). pp. 23377-23385. doi:10.1074/jbc.M602678200 ISSN 0021-9258.
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Official URL: http://dx.doi.org/10.1074/jbc.M602678200
Abstract
The plant toxin ricin is synthesized in castor bean seeds as an endoplasmic reticulum (ER)-targeted precursor. Removal of the signal peptide generates proricin in which the mature A- and B-chains are joined by an intervening propeptide and a 9-residue propeptide persists at the N terminus. The two propeptides are ultimately removed in protein storage vacuoles, where ricin accumulates. Here we have demonstrated that the N-terminal propeptide of proricin acts as a nonspecific spacer to ensure efficient ER import and glycosylation. Indeed, when absent from the N terminus of ricin A-chain, the non-imported material remained tethered to the cytosolic face of the ER membrane, presumably by the signal peptide. This species appeared toxic to ribosomes. The propeptide does not, however, influence catalytic activity per se or the vacuolar targeting of proricin or the rate of retrotranslocation/degradation of A-chain in the cytosol. The likely implications of these findings to the survival of the toxin-producing tissue are discussed.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Journal or Publication Title: | JOURNAL OF BIOLOGICAL CHEMISTRY | ||||
Publisher: | AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC | ||||
ISSN: | 0021-9258 | ||||
Official Date: | 18 August 2006 | ||||
Dates: |
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Volume: | 281 | ||||
Number: | 33 | ||||
Number of Pages: | 9 | ||||
Page Range: | pp. 23377-23385 | ||||
DOI: | 10.1074/jbc.M602678200 | ||||
Publication Status: | Published |
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