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Nucleus-encoded precursors to thylakoid lumen proteins of Euglena gracilis possess tripartite presequences
R Vacula1, J M Steiner, J Krajcovic
1Institute of Molecular and Subcellular Biology, Comenius University, Bratislava, Slovak Republic.
Abstract:
The complete presequences of the nucleus-encoded precursors to two proteins, cytochrome c6 and the 30-kDa protein of the oxygen-evolving complex, that reside in the thylakoid lumen of the chloroplasts of Euglena gracilis are presented. Sorting of these proteins involves translocation across four membranes, the three-membraned chloroplast envelope and the thylakoid membrane. The tripartite presequences show the structure: signal sequence transit sequence signal sequence. Three hydrophobic domains become apparent: two of them correspond to signal sequences for translocation across the endoplasmic reticulum (ER) membrane and the thylakoid membrane, respectively, whereas the third constitutes the stop-transfer signal contained in the long stroma-targeting part of the tripartite presequence.
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