Glycoproteins forms

The dogma that glycoproteins occur exclusively in eucaryotic cells had to be revised in the last twenty years. Bacterial glycoproteins form the outer surface (S)-layer of archae- and eubacteria [61,62]. In analogy to eucaryotic cells, partly sulfated oligosaccharides attached to Asn or Thr are found in halobacteria. Nucleoside-diphosphate-activated oligosaccharides were identified as intermediates in the biosynthesis of the S-layer of the eubacterium Bacillus alvei [63] and the archaebacterium Methanothermus fervidus [64],... 

The six membrane-spanning loops of the P-glycoprotein form a central channel for the ATP-dependent pumping of drugs from the cell. 

The alphaviruses are a group of 26 icosahedral, positive-sense RNA viruses primarily transmitted by mosquitoes [64]. These 700-A-diameter viruses are some of the simplest of the membrane-enveloped viruses, and members of this group cause serious tropical diseases with characteristic symptoms such as myositis, fever, rash, encephalitis, and polyarthritis [65]. The structures of two different alphavirus-Fab complexes have been determined by cryo-TEM Ross River virus (RR) and Sindbis virus (SIN) [66]. The amino acid sequences of the RR and SIN virus structural and nonstructural proteins are 49 and 64% identical, respectively [67]. The viral RNA genome and 240 copies of the capsid protein form the nucleocapsid core [68-73], and the El and E2 glycoproteins form heterodimers that associate as 80 trimeric spikes on the viral surface. Native SIN and RR lack the E3 glycoprotein because it disassociates from the spike complex after its display on the plasma membrane surface [74, 75]. El has a putative fusion domain that may facilitate host membrane penetration [76, 77]. E2 contains most of the neutralizing epitopes and is also probably involved in host cell recognition [78-80]. 

Integrins are adhesion molecules involved in cell-matrix interaction. Integrins are heterodimeric membrane glycoproteins formed by the combination of an a- and p-subunit with an intracellular and an extracellular domain [115]. In the brain, endothelial cells, astrocytes, and the basal membrane such as laminin and collagen contribute to form the... 

Loo.T.W, Bartlett, M.C., and Clarke, D.M. (2006) Transmembrane segment 1 of human P-glycoprotein forms part of the drtrg-binding pocket The Biochemical Journal, 399, 351-359. 

Molinari, M., and Helenius, A. (1999). Glycoproteins form mixed disulphides with oxidoreductases during folding in living cells. Nature 402, 90-93. 

Replication of various viruses in cells may also be inhibited by exposure of cells to interferon. Interferon is a glycoprotein formed by cells themselves when they are exposed to specific inducers. The most effective synthetic inducers of interferon are found between nucleic acids and polynucleotides. Electroneutral polyvinyl analogs of nucleic acids are incapable of inducing interferon in cells in culture (10). On the other hand, the complex of polyvinyl-l-cytosine with a polynucleotide, polyinosinic acid, is a very effective inducer of interferon (11). A principal reason for this effectiveness may be a high uptake of this complex by cells (10). 

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