title: A plant secretory signal peptide targets plastome-encoded recombinant proteins to the thylakoid membrane.
abstract: Plastids are considered promising bioreactors for the production of recombinant proteins, but the knowledge of the mechanisms regulating foreign protein folding, targeting, and accumulation in these organelles is still incomplete. Here we demonstrate that a plant secretory signal peptide is able to target a plastome-encoded recombinant protein to the thylakoid membrane. The fusion protein zeolin with its native signal peptide expressed by tobacco (Nicotiana tabacum) transplastomic plants was directed into the chloroplast thylakoid membranes, whereas the zeolin mutant devoid of the signal peptide, Δzeolin, is instead accumulated in the stroma. We also show that zeolin folds in the thylakoid membrane where it accumulates as trimers able to form disulphide bonds. Disulphide bonds contribute to protein accumulation since zeolin shows a higher accumulation level with respect to stromal Δzeolin, whose folding is hampered as the protein accumulates at low amounts in a monomeric form and it is not oxidized. Thus, post-transcriptional processes seem to regulate the stability and accumulation of plastid-synthesized zeolin. The most plausible zeolin targeting mechanism to thylakoid is discussed herein.
authors: Istituto di Genetica Vegetale, Consiglio Nazionale delle Ricerche (CNR), via della Madonna Alta 130, 06128 Perugia, Italy.
authors: Francesca
authors: F
authors: De Marchis
authors: Andrea
authors: A
authors: Pompa
authors: Roberta
authors: R
authors: Mannucci
authors: Tomas
authors: T
authors: Morosinotto
authors: Michele
authors: M
authors: Bellucci
mesh_terms: D010940:Plant Proteins / Q000378:metabolism*; D017510:Protein Folding; D021382:Protein Sorting Signals; D011994:Recombinant Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*; D014026:Nicotiana / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins