Poster: Protein Targeting & Vesicular Trafficking
Abs #
1194: Internalization of membrane proteins into the protein storage vacuole (PSV)
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Presenter: |
Oufattole, Mohammed , oufattol@mail.wsu.edu |
Authors | Oufattole, Mohammed (A) Jiang, Liwen (B) Rogers, John C (A) | | Affiliations: |
(A): Institute of Biological Chemistry, Washington State University
(B): Department of Biology, the Chinese University of Hong Kong
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The PSV is a compound organelle that packages, within the boundaries of the same tonoplast, storage and lytic compartments. The storage compartment contains both integral membrane proteins, assembled in a complex membrane-containing crystalloid, and soluble proteins that represent the vacuole's matrix. In an attempt to understand how membranes are internalized into the PSV's crystalloid, we have studied the targeting specificity of an integral membrane reporter protein whose final destination is the crystalloid. We have shown that a short cytoplasmic sequence, PIEPPPHH, carries all the information necessary for internalization of the reporter into the crystalloid. A type II membrane protein, SRC2, was isolated for its ability to specifically interact with PIEPPPHH both in a yeast two-hybrid system and in an in vitro system. SRC2 is comprised of a long N-terminal cytoplasmic region, a transmembrane domain, and a short lumenal sequence. Subcellular fractionation showed that SRC2 is localized in part on ER/Golgi membranes, where its cytoplasmic portion is protease sensitive, and mainly in a vacuolar fraction, where it is internalized within the vacuoles and becomes protease resistant. Immunofluorescence studies demonstrate that SRC2 colocalises with our reporter protein on vacuolar compartments. Overexpression of the cytoplasmic portion of SRC2 causes the reporter protein to be partially degraded in vacuoles. Thus, SRC2 may participate in membrane internalization and packaging within PSV precursors. Its transmembrane and lumenal sequences are highly conserved among homologs from different plants and may play an important role in this process.
