Transport of ricin and 2S albumin precursors to the storage vacuoles of Ricinus communis endosperm involves the Golgi and VSR-like receptors
We have studied the transport of proricin and pro2S albumin to the protein storage vacuoles of developing castor bean (Ricinus communis L.) endosperm. Immunoelectron microscopy and cell fractionation reveal that both proteins travel through the Golgi apparatus and co-localize throughout their route to the storage vacuole. En route to the PSV, the proteins co-localize in large (>200 nm) vesicles, which are likely to represent developing storage vacuoles. We further show that the sequence-specific vacuolar sorting signals of both proricin and pro2SA bind in vitro to proteins that have high sequence similarity to members of the VSR/AtELP/BP-80 vacuolar sorting receptor family, generally associated with clathrin-mediated traffic to the lytic vacuole. The implications of these findings in relation to the current model for protein sorting to storage vacuoles are discussed.
Document Type: Research Article
Affiliations: 1: Research School of Biological and Molecular Sciences, Oxford Brookes University, Gipsy Lane Campus, Oxford OX3 0BP, UK 2: Mass Spectrometry Unit, DIBIT-HSR, via Olgettina 58, 20132 Milan, Italy 3: Istituto di Biologia e Biotecnologia Agraria, CNR, via Bassini 15, 20133 Milan, Italy
Publication date: September 1, 2004