Proteins plasma membrane

Gram-negative bacteria are surrounded by two membranes, an inner plasma membrane and an outer membrane. These are separated by a periplasmic space. Most plasma membrane proteins contain long, continuous sequences of about 20 hydrophobic residues that are typical of transmembrane a helices such as those found in bacteriorhodopsin. In contrast, most outer membrane proteins do not show such sequence patterns. 

Signal-transducing receptors are plasma membrane proteins that bind specific molecules, such as growth factors, hormones, or neurotransmitters, and then transmit a signal to the cell s interior, causing the cell to respond in a... 

FIGURE 15.21 Hormone (H) binding to its receptor (R) creates a hormone receptor complex (H R) that catalyzes GDP-GTP exchange on the o -subunit of the heterotrimer G protein (G ), replacing GDP with GTP. The G -subunit with GTP bound dissociates from the /37-subunits and binds to adenylyl cyclase (AC). AC becomes active upon association with G GTP and catalyzes the formation of cAMP from ATP. With time, the intrinsic GTPase activity of the G -subunit hydrolyzes the bound GTP, forming GDP this leads to dissociation of G GDP from AC, reassociation of G with the /Sy subunits, and cessation of AC activity. AC and the hormone receptor H are integral plasma membrane proteins G and G are membrane-anchored proteins. 

KELL blood group antigen is a plasma membrane protein isolated from red cells homologous to zinc-binding glycoproteins with neutral endopeptidase activity. 

Receptor Broadly applied to the molecular site of drug action. More specifically, this term describes the plasma membrane proteins to which neurotransmitters, agonists and antagonists bind. 

This is an important observation given that plasma membrane proteins are often used as markers of disease. This experiment demonstrated that shotgun proteomic analysis could be successfully performed on microdis-sected, formalin-fixed tissues using the antigen retrieval method with a sensitivity equal to that of analysis of the soluble fraction of a fresh-frozen sample. 

Zeheb, R., Chang, V., and Orr, G.A. (1983) An analytical method for the selective retrieval of iminobi-otin-derivatized plasma membrane proteins. Anal. Biochem. 129, 156-161. 

To diffuse rapidly in the plane of the membrane (lateral diffusion), a molecule must simply move around in the lipid environment (including the polar head groups). It need not change how it interacts with phospholipids or with water since it is constantly exposed to pretty much the same environment. Lateral diffusion can be slowed (or prevented) by interactions between membrane proteins and the cellular cytoskeleton. This spatially restricts a plasma membrane protein to a localized environment. 

Plasma membrane proteins are sorted to their final destinations at the trans-Golgi network 150... 

Proteins that reversibly associate with synaptic plasma membrane proteins... 

Schloss, R, Mayser, W and Betz, H. (1992) Neurotransmitter transporters. A novel family of integral plasma membrane proteins. FEBS Lett. 307,76-78. 

The G-protein that has been termed Gp, and that is linked to phospholipase C activation, may in fact be Gaj 2 or Gc. 3. Ga is designated as the G-protein responsible for activation of phospholipase A2, which results in arachidonic acid release. Some experimental evidence indicates that, at least in HL-60 cells, different agonists can preferentially activate different phospholipases, and some of these are responsible for the activation of secretion. In neutrophils, the two pertussis-toxin-sensitive Ga-proteins (Gaj-2 and G j 3) have been identified by peptide mapping of proteolytic digests of the proteins, by peptide sequencing and by immunoblotting. Complementary-DNA clones for the mRNA of these two molecules have also been isolated from an HL-60 cDNA library. Gai-2 is five to ten times more abundant than Gai.3, the former component comprising 3% of the total plasma membrane proteins. It is possible that these two different Ga-subunits are coupled to different phospholipases (e.g. phospholipases C and D). Pertussis toxin inhibits the secretion of O2 after stimulation of neutrophils by fMet-Leu-Phe, but pertussis-toxin-insensitive G-proteins are also present in neutrophils. These may be members of the Gq family and may be involved in the activation of phospholipase Cp (see 6.3.1). 

Rat serum and plasma membrane proteins Design of the monolith cartridge, purification, comparison with conventional columns Anion Exchange, Affinity (Heparin) [45]... 

Many cells have an asymmetric structure because of the necessity for function (Drubin and Nelson, 1996). For example, (the outer surface of) the plasma membrane of epithelial cells is fenced by a tight junction so that the lipids are separated between the apical part and the basolateral part (Fig. 9) (Eaton and Simons, 1995). Therefore, some molecular mechanisms must exist to sort the plasma membrane proteins into these two parts. Some signals related to the secretory/endocytic pathways have been found important (Matter and Mellman, 1994). Their details are not described here because the area is too specific for predictive purposes. 

R. Deubiquitination step in the endocytic pathway of yeast plasma membrane proteins crucial role of Doa4p ubiquitin isopeptidase, Mol Cell Biol, 2001, 21, 4482-94. 

Liposomes reconstituted with exogenous plasma membrane proteins can be microinjected into the cytoplasm, resulting in the expression of functional proteins in the oocyte membrane (Le Caherec et al., 1996). 

Ubiquitination reaction is reversible like phosphorylation until the ubiquitinated protein is committed to degradation by the proteasome. The reversibility is less clear with respect to endocytotic degradation, that is, internalization of plasma membrane proteins through endocytosis and their degradation through the lysosome. 

TF3AF6, plasma membrane proteins Free Ub Cyclin B1... 

Galan, J., and R. Haguenauer-Tsapis. Ubiquitin lys63 is involved in ubiquitination of a yeast plasma membrane protein. Embo J. 16 5847-54.1997. 

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