Glycoproteins, type

In antigens of the glycan and glycoprotein types the immuno-determinant groups are very often terminal carbohydrate moieties. 

In the pig, isoprenaline caused a significant increase in the number of goblet cells in the bronchial epithelium, but there was no change in their glycoprotein type, most containing exclusively sialomu-cin (Baskerville 1976). 

Glycoproteins or mucoproieins. Compounds of proteins with carbohydrates. All glycoproteins contain a hexosamine and usually sulphate, ethanoate and glucuronic acid. The carbohydrate-protein linkages are, in some cases covalent and in others of the salt type. Aqueous solutions of glycoproteins are extremely viscous. 

A variety of cellular and viral proteins contain fatty acids covalently bound via ester linkages to the side chains of cysteine and sometimes to serine or threonine residues within a polypeptide chain (Figure 9.18). This type of fatty acyl chain linkage has a broader fatty acid specificity than A myristoylation. Myristate, palmitate, stearate, and oleate can all be esterified in this way, with the Cjg and Cjg chain lengths being most commonly found. Proteins anchored to membranes via fatty acyl thioesters include G-protein-coupled receptors, the surface glycoproteins of several viruses, and the transferrin receptor protein. 

FIGURE 9.26 The carbohydrate tnoiedes of glycoproteins may be linked to the protein via (a) serine or threonine residues (in the O-linked saccharides) or (b) asparagine residues (in the N-linked saccharides), (c) N-Linked glycoproteins are of three types high mannose, complex, and hybrid, the latter of which combines structures found in the high mannose and complex saccharides. 

LC-MS with on-line SPE using a RAM pre-column with an internal ODS phase was described by van der Hoeven et al. (95) for the analysis of cortisol and prednisolone in plasma, and arachidonic acid in urine. The samples were injected directly and the only off-line pretreatment required was centrifugation. By using the on-line SPE-LC-MS system, cortisol and related compounds could be totally recovered and quantified in 100 p.1 plasma within 5 min with a typical detection of 2 ng/ml (Figure 11.6(b)). The RAM-type of sorbents, in which the outer surface of the particles is covered with aj-acid glycoprotein, also appear to be useful for direct SPE of... 

Neuraminidase inhibitors are the major class of drugs to treat or to prevent the infection with influenza viruses. Currently, two neuraminidase inhibitors are available, zanamivir and oseltamivir, which block the release of new influenza vims from infected host cells and thereby stop the spread of infection. The enzyme neuraminidase is a surface glycoprotein present on all influenza viruses. There are nine influenza neuraminidase sub-types known of which subtypes N1 and N2 appear to be the most important ones. Neuraminidase inhibitors are effective against all neuraminidase subtypes. The activity of the neuraminidase is required for the newly... 

The three selectins are related both structurally and functionally. They are transmembrane proteins, with an N-terminal C-type actin domain, followed by an EGF repeat and a variable number of complement control protein (CCP) domains. Selectins bind carbohydrates, which are present in various glycoproteins. 

Tissue-type plasminogen activator (tPA) is a glycoprotein (68 kDa), synthesized by endothelial and tumor-cells. As a serine protease, tPA hydrolyses Arg561-Val562 peptide bond in plasminogen, resulting in plasmin formation. It needs cofactors for efficient plasminogen activation. 

Urokinase-type plasminogen activator (uPA, urokinase) is synthesized by endothelial and tumor cells as a single-chain glycoprotein (scuPA) without catalytic activity. When it is converted to a two-chain protein (tcuPA) by plasmin, an active serine protease center develops, which activates plasminogen. Thus, uPA (55 kDa) results in the amplification of fibrinolysis. 

Both of the studies involving glycoproteins have employed Q-ToF mass spectrometers and both sets of anthors comment on the sensitivity of this type of instrument, allowing nsefnl data to be obtained from the limited amonnts of sample usually available from natural sources. 

Many enveloped viruses share a common mechanism of fusion, mediated by a virus-encoded glycoprotein that contains heptad repeats in its extraceUnlar domain. Dnring the fnsion process, these domains rearrange to form highly structured and thermodynamically stable coiled-coils. Viruses encoding fusion proteins that have these domains inclnde members of the paramyxovirus family (e.g., respiratory syncytial virus, metapneumovirus, and measles virus), ebola virus, influenza, and members of the retroviridae (e.g., human T cell lenkemia virus type-1 and human immunodeficiency virus type-1, HlV-1). Peptide inhibitors of fusion that disrupt the... 

He Y, Vassell R, Zaitseva M, Nguyen N, Yang Z, Weng Y, Weiss CD (2003) Peptides trap the human immunodeficiency virus type 1 envelope glycoprotein fusion intermediate at two sites. J Virol 77 1666-1671... 

Lu J, Sista P, Giguel F, Greenberg M, Kuritzkes DR (2004) Relative replicative fitness of human immunodeficiency virus type 1 mutants resistant to enfuvirtide (T-20), J Virol 78 4628 637 Lu M, Blacklow SC, Kim PS (1995) A tiimeric structural domain of the HlV-1 transmembrane glycoprotein, Nat Struct Biol 2 1075-1082... 

A key requirement of QSAR is that the compounds used in the modeling and prediction processes should have the same mechanism of action, and for this reason most QSAR studies are made with congeneric series of compounds. However, if a diverse set of compounds can reasonably be assumed to have the same mechanism of action, QSAR modeling can justihably be carried out. For example, Dearden et al. [43] developed a QSAR for the ratio of brain levels of 22 very diverse drugs in the wild-type mouse and the P-glycoprotein knockout mouse (R+/ ) ... 

Types Steroids, iodothyro-nines, calcitriol, retinoids Polypeptides, proteins, glycoproteins, catecholamines... 

N-Acetylneur-aminic acid Sialic acid (nine C atoms) NeuAc CMP-NeuAc Often the terminal sugar in both N- and 0-linked glycoproteins. Other types of sialic acid are also found, but NeuAc is the major species found in humans. Acetyl groups may also occur as 0-acetyl species as well as N-acetyl. 

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