Membrane proteins endoplasmic reticulum

Hampton, R. Y., R. G. Gardner, and J. Rine, Role of 26S proteasome and HRD genes in the degradation of 3-hydroxy-3-methylglutaryl-CoA reductase, an integral endoplasmic reticulum membrane protein. Md Biol Cell, 1996, 7(12), 2029 4. 

Glazner G.W., and Fernyhough P. 2002 Neuronal survival in the balance are endoplasmic reticulum membrane proteins the fulcrum Cell Calcium 32, 421-433. 

Gaynor, E. C., Mondesert, G., Grimme, S.J., Reed, S. I., Orlean, P., and Emr, S. D. (1999). MCD4 encodes a conserved endoplasmic reticulum membrane protein essential for glycosylphosphatidylinositol anchor synthesis in yeast. Mol. Biol. CeU 10, 627-648. 

Santiago, T. C., Zufferey, R., Mehra, R. S., Coleman, R. A., and Mamoun, C. B. (2004). The Plasmodium falciparum PfGATP is an endoplasmic reticulum membrane protein important for the initial step of malarial glycerolipid synthesis. /. Biol. Chem. 279,9222-9232. 

Kandasamy, P., Vemula, M., Oh, C.S., Chellappa, R. and Martin, C.E. Regulation of unsaturated fatty acid biosynthesis in Saccharomyces. the endoplasmic reticulum membrane protein, Mga2p, a transcription activator of the OLEl gene, regulates the stability of the OLEl mRNA through exosome-mediated mechanisms. J Biol Chem, 279 (2004) 36586-36592. 

This impressive reaction is catalyzed by stearoyl-CoA desaturase, a 53-kD enzyme containing a nonheme iron center. NADH and oxygen (Og) are required, as are two other proteins cytochrome 65 reductase (a 43-kD flavo-protein) and cytochrome 65 (16.7 kD). All three proteins are associated with the endoplasmic reticulum membrane. Cytochrome reductase transfers a pair of electrons from NADH through FAD to cytochrome (Figure 25.14). Oxidation of reduced cytochrome be, is coupled to reduction of nonheme Fe to Fe in the desaturase. The Fe accepts a pair of electrons (one at a time in a cycle) from cytochrome b and creates a cis double bond at the 9,10-posi-tion of the stearoyl-CoA substrate. Og is the terminal electron acceptor in this fatty acyl desaturation cycle. Note that two water molecules are made, which means that four electrons are transferred overall. Two of these come through the reaction sequence from NADH, and two come from the fatty acyl substrate that is being dehydrogenated. 

Walter, P., andjohnson, A. E. (1994). Signal sequence recognition and protein targeting to the endoplasmic reticulum membrane. Annu. Rev. Cell Biol. 10, 87—119. 

Passage through the Golgi apparatus is obligatory for most proteins destined for fast transport. In all cell types, secretory and integral membrane proteins are synthesized on polysomes bound to the endoplasmic reticulum. Secretory proteins enter the lumen of the reticulum, whereas membrane proteins become oriented within the... 

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. 

T. Friedberg, R. Holler, B. Lollmann, M. Arand, F. Oesch, The Catalytic Activity of the Endoplasmic Reticulum-Resident Protein Microsomal Epoxide Hydrolase towards Carcinogens Is Retained on Inversion of Its Membrane Topology , Biochem. J. 1996, 319, 131 - 136. 

Mayer TU, Braun T, Jentsch, S (1998) Role of the proteasome in membrane extraction of a short-lived ER-transmembrane protein. EMBO ] 17 3251-3257 McCracken AA, Brodsky JL (1996) Assembly of ER-associated protein degradation in vitro dependence on cytosol, calnexin, and ATP. J Cell Biol 132 291-298 McDonald HB, Byers B (1997) A proteasome cap subunit required for spindle pole body duplication in yeast. J Cell Biol 137 539-553 McGee TP, Cheng HH, Kumagai H, Omura S, Simoni RD (1996) Degradation of 3-hydroxy-3-methylg utaryl-CoA reductase in endoplasmic reticulum membranes is accelerated as a result of increased susceptibility to proteolysis. J Biol Chem 271 25630-25638... 

Intracellular antigens could be modified internal proteins, which are continuously removed by the cell, the structure altered and attached to MHC I. This takes place in the rough endoplasmic reticulum. The protein/pep tide-hapten fragments are then presented to the external surface of the cell membrane as a complex with the MHC I. Then cytotoxic T cells (CD8+) accept the protein/peptide and destroy the cell. This mechanism gives rise to a type IV response. 

Figure 32-4 Sketch illustrating only a few of the many aspects of apoptosis in a mammalian cell. Emphasis here is on the death receptor pathways and cytochrome c-activated apoptosis. A third pathway is initiated by stress in endoplasmic reticulum membranes. In addition, attack by cytolytic T cells sometimes causes apoptosis by action of a granzyme on protein Bid or via a death receptor. Objects in scheme are not drawn to a single scale.

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

RNA polymerase III (RNA Pol III) is also located in the nucleoplasm. It transcribes the genes for tRNA, 5S rRNA, U6 snRNA, and the 7S RNA associated with the signal recognition particle (SRP) involved in the translocation of proteins across the endoplasmic reticulum membrane (see Topic H4). 

Members of the Bcl-2 family share one or more Bcl-2 homology (BFI) domains, named BFI1, BFI2, BFI3, and BFI4 (Adams and Cory, 1998). It is not yet clear which structural features determine if these proteins possess pro- or anti-apoptotic activities. However, some studies revealed that the BH3 domain is a critical domain for the proapoptotic members (Chittenden et al., 1995). Besides BH domains, some contain a hydrophobic domain in the C-terminal region, which is essential for the attachment to intracellular membranes, like the outer mitochondrial, nuclear, and endoplasmic reticulum membranes (Krajewski et al., 1993 Nguyen et al., 1993). 

Endoplasmic reticulum Membrane-enclosed channels Involved in transport of proteins for extracellular secretion and modification or detoxification of chemicals... 

LDL binds specifically to lipoprotein receptors on the cell surface. The resulting complexes become clustered in regions of the plasma membrane called coated pits. Endocytosis follows (see Fig. 13-3). The clathrin coat dissociates from the endocytic vesicles, which may recycle the receptors to the plasma membrane or fuse with lysosomes. The lysosomal proteases and lipases then catalyze the hydrolysis of the LDL-receptor complexes the protein is degraded completely to amino acids, and cholesteryl esters are hydrolyzed to free cholesterol and fatty acid. New LDL receptors are synthesized on the endoplasmic reticulum (ER) membrane and are subsequently reintroduced into the plasma membrane. The cholesterol is incorporated in small amounts into the endoplasmic reticulum membrane or may be stored after esterification as cholesteryl ester in the cytosol this occurs if the supply of cholesterol exceeds its utilization in membranes. Normally, only very small amounts of cholesteryl ester reside inside cells, and the majority of the free cholesterol is in the plasma membrane. 

A close look at the events which occur during the lag period In GA Induction of novo synthesis of new enzymes has provided some Important clues as to whether GA acts at the transcriptional or translational level (16 and papers cited therein). An increase in polyribosome formation and an increased synthesis of ribosomes and endoplasmic reticulum membranes were found. All of these effects begin within 2 to 4 hr after application of GA. Their observations led Evins and Varner (16) to conclude that the GA-stimulated increases in the number of monoribosomes and the percentage of polyribosomes probably are prerequisite for the hormone induction of protein synthesis. 

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