Anchor protein

H-bonds between sugar-phosphate backbone and protein help anchor protein to DNA... 

Myristic acid may be linked via an amide bond to the a-amino group of the N-terminal glycine residue of selected proteins (Figure 9.18). The reaction is referred to as A -myristoylation and is catalyzed by myristoyl—CoAtprolein N-myris-toyltransferase, known simply as NMT. A -Myristoyl-anchored proteins include the catalytic subunit of cAMP-dependent protein kinase, the ppSff tyrosine kinase, the phosphatase known as calcineurin B, the a-subunit of G proteins (involved in GTP-dependent transmembrane signaling events), and the gag proteins of certain retroviruses, including the FHV-l virus that causes AIDS. 

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. 

The Molecular Defect in Dnchenne Muscular Dystrophy Involves an Actin-Anchoring Protein... 

Langeberg LK, Scott JD (2005) A-kinase-anchoring proteins. J Cell Sci 118 3217-3220... 

Beene DL, Scott JD (2007) A-kinase anchoring proteins take shape. Curr Opin Cell Biol 19 192-198... 

AKAPs are cyclic AMP-dependent protein kinase (PKA)-anchoring proteins, a family of about 30 proteins anchoring PKA at subcellular sites in close vicinity to a certain substrate. 

GPI anchoring is a posttranslational modification occurring in the endoplasmic reticulum where preassembled GPI anchor precursors are transferred to proteins bearing a C-terminal GPI signal sequence. The GPI anchor precursors are synthesized in the endoplasmic reticulum by sequential addition of sugar and other components to phosphatidylinositol. Protein GPI anchors are ubiquitous in eukaryotic cells. In mammalian cells, GPI anchored proteins are often found in lipid rafts which are subdomains of the plasma membrane, containing various signaling components. 

GPI-anchored proteins constitute a quite diverse family of cell-surface molecules that participate in such processes as nutrient uptake, cell adhesion, and membrane signaling events [3]. All GPI-linked proteins are destined for the cell surface via trafficking through the secretory pathway, where they acquire the... 

PPCs Prenylation is the post-translational addition of 15- or 20-carbon isoprenyl lipids to the C-terminus of proteins. Prenylation is an irreverable modification that anchors proteins to the membrane fraction of cells. 

Numerous protein phosphatases are targeted to their substrates and regulators through the interaction with specific scaffolding proteins. Some of these anchoring proteins bind both, kinases and phosphatases. This applies to ser/thr protein phosphatases as well as to tyrosine phosphatases. 

Paroxysmal nocturnal hemoglobinemia (MIM 311770) Mutations in the PIG-A gene, affecting synthesis of GPI-anchored proteins... 

Kenworthy, A. K., Petranova, N. and Edidin, M. (2000). High resolution FRET microscopy of cholera toxin B-subunit and GPI-anchored proteins in cell plasma membranes. Mol. Biol. Cell 11, 1645-55. 

Friedrichson, T., and Kurzchalia, T.V. (1998) Microdomains of GPI-anchored proteins in living cells revealed by crosslinking. Nature 394(6695), 802-805. 

Membranes are asymmetric. Integral membrane proteins can t be washed off. Peripheral membrane proteins can be washed off. Membrane spanning segments and lipid modification (fatty acylation and prenylation), anchor proteins in a fluid bilayer (Singer fluid mosaic model). 

Much of the plasma membrane cholesterol is removed by incubating cells with P-methylcyclodextrin for several hours. Cells remain viable after this treatment but the raft fraction is reduced and it is inferred that the depleted proteins are normally associated with cholesterol-dependent lipid rafts. Some, but not all, glycosylphosphatidylinositol (GPI)-anchored proteins are recovered in the fractions defined by this procedure. 

GPI-anchored proteins (GP-APs) are synthesized in the cytoplasm and their transport into the ER occurs during the process of acquiring a GPI anchor, which is ultimately sorted into the outer leaflet of plasma membranes [24], A FRET study of fluorophore-labeled GPI-APs in cultured... 

Sharma, P., Varma, R., Sarasij, R. C., Gousset, K., Krishnamoorthy, G. and Rao M, Mayor S. Nanoscale organization of multiple GPI-anchored proteins in living cell membranes. Cell 116 577-589, 2004. 

A bacterial phosphatidylinositol specific phospholipase C (PI-PLC) had been available for many years before it was demonstrated to strip a number of membrane-bound proteins from eukaryotic cell surfaces [1], Such proteins are anchored by a PI moiety in which the 6 position of inositol is glycosidically linked to glucosamine, which in turn is bonded to a polymannan backbone (Fig. 3-10). The polysaccharide chain is joined to the carboxyl terminal of the anchored protein via amide linkage to ethanolamine phosphate. The presence of a free NH2 group in the glucosamine residue makes the structure labile to nitrous acid. Bacterial PI-PLC hydrolyzes the bond between DAG and phosphati-dylinositols, releasing the water-soluble protein polysac charide-inositol phosphate moiety. These proteins are tethered by glycosylphosphatidylinositol (GPI) anchors. 

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