Components Involved in Protein Translocation Across the Membrane of the Endoplasmic Reticulum
Proteins which are synthesized in the cytoplasm of eucaryotic cells can have different destinations. They can remain in the cytoplasm or be transported to a particular organelle such as the endoplasmic reticulum (ER), the mitochondria or the nucleus. The ER is the entry site to the secretory pathway for secretory, lysosomal and for those membrane proteins that become resident of the ER, the Golgi or the plasma membrane. Proteins which enter this pathway have signal sequences that guide them to the ER membrane. A typical signal sequence is about 20 amino acid residues long and its main distinctive feature is a core of hydrophobic amino acid residues. On the luminal side of the membrane the signal sequence of most presecretory proteins is cleaved by signal peptidase.
KeywordsProtein Translocation Microsomal Membrane Signal Recognition Particle Signal Peptidase Docking Protein
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- Hikawa, A., Hashimoto, M., Horigome, T., Omata, S. and Sugano, H. (1985) Properties of rat liver signal peptidase reconstituted into liposomes. I. Biochem. 97: 105–112Google Scholar
- Ibrahimi, I. and Fuchs, E. (1987) Nascent secretory polypeptides synthesized on Escherichia coli ribosomes are not translocated across mammalian endoplasmic reticulum. I. Bacteriol. 169: 1603–1610Google Scholar
- Kreibich, G., Czako-Graham, M., Grebenau, R., Mok, W., Rodriguez-Boulan, E. and Sabatini, D.D. (1978) Characterization of the ribosomal binding site in rat liver rough microsomes: Ribophorins I and II, two integral membrane proteins related to ribosome binding. J. Supramolec. Structure 8: 279–302CrossRefGoogle Scholar
- Kreibich, G., Marcantonio, E. E. and Sabatini, D. D. (1983) In: Methods Enzymology, Academic Press, New York (S. Fleischer and B. Fleischer, eds.), 96: 520–530Google Scholar
- Marcantonio, E. E., Amar-Costesec, A. and Kreibich, G. (1982) Segregation of the polypeptide translocation apparatus to regions of the endoplasmic reticulum containing ribophorins and ribosomes. II. Rat liver microsomal subfractions contain equimolar amounts of ribophorins and ribosomes. J. Cell Biol. 99: 2254–2259CrossRefGoogle Scholar
- Rapoport, T.A. and Wiedmann, M. (1985) Application of the signal hypothesis to the incorporation of integral membrane proteins. Current topics in membranes and transport. 24: 1–63Google Scholar
- von Heijne, G. (1985) Structural and thermodynamic aspects of the transfer of proteins into and across membranes. Current topics in membranes and transport, 24: 151–179Google Scholar
- Walter, P. and Blobel, G. (1981a) Translocation of proteins across the endoplasmic reticulum II. Signal recognition protein (SRP) mediates the selective binding to microsomal membranes of in-vitro-assembled polysomes synthesizing secretory protein. J. Cell Biol. 91: 551–556PubMedCrossRefGoogle Scholar
- Walter, P. and Blobel, G. (1981b) Translocation of proteins across the endoplasmic reticulum. III. Signal recognition protein (SRP) causes signal sequence-dependent and site-specific arrest of chain elongation that is released by microsomal membranes. J. Cell Biol. 91: 557–561PubMedCrossRefGoogle Scholar