Protein translocation, endoplasmic

Kuroiwa, T., Sakaguchi, M., Mihara, K., and Omura, T. (1991). Systematic analysis of stop-transfer sequence for microsomal membrane. Biol. Chem. 266, 9251—9255. Kuroiwa, T., Sakaguchi, M., Omura, T., and Mihara, K. (1996). Reinitiation of protein translocation across the endoplasmic reticulum membrane topogenesis of multispan-ning membrane proteins. J. Biol. Chem. 271, 6243—6248. 

Sommer, T. and Jentsch, S. A protein translocation defect linked to ubiquitin conjugation at the endoplasmic reticulum. Nature 1993, 365, 176-79. 

The phosphatidylcholine in bile is synthesised in the endoplasmic reticulum of the hepatocyte and must be transported to the canalicular membrane. One possibility involves the nonspecific phosphatidylcholine transfer protein but a mouse null for this protein did not show reduced phosphatidylcholine secretion into bile and there was no compensatory increase in other phospholipids transfer proteins. However, the plasma membrane would receive a ready supply of phospholipid by insertion of vesicles, and the MDR3 protein translocates this molecule from the inner leafiet to the outer surface where there is contact with bile acids, as suggested by Smit and colleagues. The role of this transporter is shown in Figure 2.2. 

Hagting A, Karlsson C, Clute P, Jackman M, Pines J (1998) MPF localization is controlled by nudear export. EMBO J 17 4127-4138 Hamman BD, Chen JC, Johnson EE, Johnson AE (1997) The aqueous pore through the translocon has a diameter of 40-60 A during cotranslational protein translocation at the ER membrane. Cell 89 535-544 Hampton RY, Rine J (1994) Regulated degradation of HMG-CoA reductase, an integral membrane protein of the endoplasmic reticulum, in yeast. J Cell Biol 125 299-312... 

Blobel discovered the mechanism for protein translocation across the endoplasmic reticulum membrane—the signal hypothesis. 

Scheper W, Thaminy S, Kais S, Stagljar I, Romisch K. Coordination of N-glycosylation and protein translocation across the endoplasmic reticnlnm membrane by Sssl protein. J. Biol. Chem. 2003 278 37998-38003. 

Tyson, J. R., and Stirling, C. J. (2000). LHS1 and SIL1 provide a lumenal function that is essential for protein translocation into the endoplasmic reticulum. EMBO J. 19,... 

Rapoport, T. A., K. E. Matlack, K. Plath, B. Misselwitz, and O. Staeck. 1999. Post-translational protein translocation across the membrane of the endoplasmic reticulum. Biol. Chem. 380 1143-1150. 

Gillece P, Pilon M, Romisch K (2000) The protein translocation channel mediates glycopeptide export across the endoplasmic reticulum membrane. Proc Natl Acad Sci USA 97 4609 -4614 Ginsberg HN (1997) Role of lipid synthesis, chaperone proteins and proteasomes in the assembly and secretion of apoprotein B-containing lipoproteins from cultured liver cells. Clin Exp Pharmacol Physiol 24 A29-A32... 

Kalies KU, Allan S, Sergeyenko T et al. (2005) The protein translocation channel binds proteasomes to the endoplasmic reticulum membrane. EMBO J 24(13), 2284-2293. 

Walter, P., and Blobel, G., 1982, Signal recognition particle contains a 7S RNA essential for protein translocation across the endoplasmic reticulum. Nature (London) 299 691. 

Rapoport, T.A., 2007. Protein translocation across the eukaryotic endoplasmic reticulum and bacterial plasma membranes. Nature, 450, 663-669. 

Krieg, U.C., Johnson, A.E., and Walter, R, Protein translocation across the endoplasmic reticulum membrane identification by photocross-Hnking of a 39-kD integral membrane glycoprotein as part of a putative translocation tunnel, /. Cell Biol., 109, 5, 2033, 1989. 

The UPS also plays a major role in protein quality control. In a process known as endoplasmic associated degradation (ERAD), misfolded proteins, which are formed in the endoplasmatic reticulum, are translocated back to the cytoplasm and degraded by the proteasome. 

From overexpression studies, it can be inferred that individual isoforms of PKC are precisely directed to distinct subcellular locations (e.g. PKCa to the endoplasmic reticulum and PKCS to the Golgi). Directing PKC isozymes to specific subcellular loci appears to occur via interaction of the enzyme with localized intracellular binding proteins. Such proteins may or may not be substrates for PKC. An example of the latter category would be RACK (receptors for activated C kinase) 1. RACKs are thought to interact only with activated PKCs and to direct translocated PKCs to specific loci. 

The site of synthesis of numerous proteins is remote from their site of function. During transfer from one site to the other, proteins must, therefore, cross cellular membranes [43] [44], Proteins are usually synthesized as precursors containing an amino terminal extension, called the signal (leader) peptide, the sequence of which contains the necessary information to guide the protein to and across a specific membrane. After transmembrane transport (called translocation), the signal peptide is cleaved off by specific signal peptidases, which are found in the rough endoplasmic reticulum, and the... 

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