Nascent proteins

One of the most studied functions of PDI is its ability to catalyze isomerization and rearrangement of disulfide bonds (Eq. (14)) in the ER contributing to a proper folding of nascent proteins (Novia et al., 1992). [Pg.101]

Glycosyladon of the p62 afad El proteins is not needed for correct assembly in the ER, since in tunicamycin-treated cells, the assembly of these nonglycosylated proteins proceeds normally (Garoff and Schwarz, 1978). The drug tunicamycin blocks the assembly of the dolichol-linked oligosaccharide intermediate so that no transfer of oligosaccharides to nascent protein is possible (Tkasz and Lampen, 1975). [Pg.111]

Answer B. Decreased Factor V secretion and a corresponding accumulation of cytoplasmic antigen suggest a defect in the translocation of the nascent protein to the endoplasmic reticulum. This implies a mutation in the N-terminal amino acid signal sequence required for targeting to the ER and encoded by the first exon of the gene. [Pg.64]

Just as pre-mRNA molecules are chemically modified to create functional mRNA (figure 13.2), nascent proteins may be chemically modified to create fully functional molecules. There are two general mechanisms at work here proteolytic cleavage and covalent modification. [Pg.175]

A modeT that accounts for the selective degradation of proteins based on the amino acid that is present on the amino- or N-end of nascent proteins. Intracellular processing of nascent, noncompartmentalized proteins generates the mature protein via the action of amino-terminal peptidases. In model studies using /3-galactosidase... [Pg.498]

Antibodies against the virus but also amantadine and derivatives, interfere with host cell penetration. There are nucleoside analogues such as aciclovir and ganciclovir, which interfere with DNA synthesis, especially of herpes viruses. Others like zidovudine and didanosine, inhibit reverse transcriptase of retroviruses. Recently a number of non-nucleoside reverse transcriptase inhibitors was developed for the treatment of HIV infections. Foscarnet, a pyrophosphate analogue, inhibits both reverse transcriptase and DNA synthesis. Protease inhibitors, also developed for the treatment of HIV infections, are active during the fifth step of virus replication. They prevent viral replication by inhibiting the activity of HIV-1 protease, an enzyme used by the viruses to cleave nascent proteins for final assembly of new vi-rons. [Pg.419]

This case is particularly relevant in regard to the formation of inclusion bodies (see Section 17.6 below) as overexpression of a target protein is a mode of obtaining the protein. With the assumption that folding and aggregation behave as in case 1, and nascent protein is expressed with a zerofh-order rate constant k0 with respect to the... [Pg.499]

The signal that directs a ribosome with its nascent protein to the ER membrane is a sequence of amino acids near the amino terminus of its nascent polypeptide chain. In a secretory protein, these signal sequences are present... [Pg.337]

The nascent protein synthesized by membrane-bound ribosomes is translocated in an ATP-drive reaction across the ER membrane into the ER lumen. [Pg.346]

The /V-formylmethionine of a nascent protein synthesized in bacteria is removed by the sequential activities of PDF and a methionine aminopeptidase to generate the mature protein. The gene encoding PDF was cloned and overexpressed in E. coli by Meinnel and coworkers (1993). The PDF enzyme has an unusual metal ion (Fe2+) as its catalyst. However, the ferrous ion in this enzyme is unstable and can be quickly and irreversibly oxidized to ferric ion, rapidly inactivating the enzyme. PDF-based assay development therefore depended on the ability of nickel ion to replace ferrous ion in vitro, increasing the stability of the enzyme and maintaining its enzymatic activity (Groche et al., 1998 Clements et al., 2001 Hackbarth et al., 2002). [Pg.126]

The question of the biosynthesis of GSHPx has been the subject of much research and it is now known with certainty that the formation of the seleno-cysteinyl residue depends on the existence of a gene that specifies a unique UGA codon that codes specifically for selenocysteine the complimentary tRNA binds serine to which is then added the selenyl moiety to form selenocysteine which is added to the nascent protein by the normal translational process [13], This mechanism has also been demonstrated for the biosynthesis of other seleno-enzymes in several bacterial species [14-16]. [Pg.118]

Prolyl isomerases of the cyclophilin type show some properties that would be expected for a catalyst of cellular protein folding. Cyclophilins occur in all cellular compartments where folding reactions occur. The activity toward accessible prolyl bonds is high, and the specificity with regard to the chemical nature of residue Xaa is low. Additional experiments are clearly needed, however, to clarify the possible role of prolyl isomerases for the in vivo folding process of nascent proteins. [Pg.61]

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