The Internal Propeptide of the Ricin Precursor Carries a Sequence-Specific Determinant for Vacuolar Sorting

Ricin is a heterodimeric toxin that accumulates in the storage vacuoles of castor bean (Ricinus communis) endosperm. Proricin is synthesized as a single polypeptide precursor comprising the catalytic A chain and the Gal-binding B chain joined by a 12-amino acid linker propeptide. Upon arrival in the...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 2001-05, Vol.126 (1), p.167-175
Main Authors: Frigerio, Lorenzo, Nicholas A. Jolliffe, Di Cola, Alessandra, Felipe, Doramys Hernández, Paris, Nadine, Neuhaus, Jean-Marc, Lord, J. Michael, Ceriotti, Aldo, Roberts, Lynne M.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Antiserum
Base Sequence
Biological and medical sciences
Cell biochemistry
Cell Biology and Signal Transduction
Cell physiology
Delta cells
DNA Primers
Endocytosis
Fundamental and applied biological sciences. Psychology
Molecular Sequence Data
Nicotiana - metabolism
Nicotiana - ultrastructure
Plant cells
Plant Lectins
Plant physiology and development
Plants, Toxic
Protein precursors
Proteins
Protoplasts
Receptors
Ricin - chemistry
Ricin - metabolism
Secretion
Sequence Homology, Amino Acid
Toxins
Transfection
Vacuoles
Vacuoles - metabolism
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Summary:Ricin is a heterodimeric toxin that accumulates in the storage vacuoles of castor bean (Ricinus communis) endosperm. Proricin is synthesized as a single polypeptide precursor comprising the catalytic A chain and the Gal-binding B chain joined by a 12-amino acid linker propeptide. Upon arrival in the vacuole, the linker is removed. Here, we replicate these events in transfected tobacco (Nicotiana tabacum) leaf protoplasts. We show that the internal linker propeptide is responsible for vacuolar sorting and is sufficient to redirect the ricin heterodimer to the vacuole when fused to the A or the B chain. This internal peptide can also target two different secretory protein reporters to the vacuole. Moreover, mutation of the isoleucine residue within an NPIR-like motif of the propeptide affects vacuolar sorting in proricin and in the reconstituted A-B heterodimer. This is the first reported example of a sequence-specific vacuolar sorting signal located within an internal propeptide.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.126.1.167