Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P11021 (BiP)
 2,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The half-time for secretion of the plasma protein C-reactive protein (CRP) by the hepatocyte decreases markedly in association with its increased synthesis during the acute phase response to tissue injury (Macintyre, S., D. Samols, and I. Kushner. 1985. J. Biol. Chem. 260:4169-4173). In studies in which subcellular fractions were prepared from cells incubated under pulse-chase conditions, CRP was found to be preferentially retained within the ER of normal hepatocytes, but secreted relatively efficiently in cells prepared from rabbits undergoing the acute phase response. On the basis of the detergent-dependency of specific binding of radiolabeled CRP, as well as EM visualization of biotinylated CRP identified with peroxidase-conjugated streptavidin, CRP was found to bind to the lumenal surface of permeabilized rough microsomes, while no binding was detected in Golgi fractions. As judged by both kinetic and equilibrium binding studies, rough microsomes from control rabbits were found to have two classes of specific binding sites for CRP; a high affinity site (Kd = 1 nM, Bmax = 1 pmol CRP/mg microsomal protein) as well as a much lower affinity (Kd = 140 nM) site. In contrast, only the lower affinity class was detected in microsomes isolated from rabbits undergoing the acute phase response. On nitrocellulose blots probed with radiolabeled CRP a 60-kD protein, distinct from BiP, was detected in extracts of rough microsomes isolated from control rabbits, but not in Golgi fractions or rough microsomes from stimulated animals. These findings correlate with previous observations of changes in secretion kinetics of CRP and are consistent with the hypothesis that the intracellular sorting of CRP could be rerouted by downregulation of a specific ER binding site during the acute phase response.
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PMID:Regulated export of a secretory protein from the ER of the hepatocyte: a specific binding site retaining C-reactive protein within the ER is downregulated during the acute phase response. 137 45

In most aerobic organisms hemoperoxidases play a major role in H(2)O(2)-detoxification, but trypanosomatids have been reported to lack this activity. Here we describe the properties of an ascorbate-dependent hemoperoxidase (TcAPX) from the American trypanosome Trypanosoma cruzi. The activity of this plant-like enzyme can be linked to the reduction of the parasite-specific thiol trypanothione by ascorbate in a process that involves nonenzymatic interaction. The role of heme in peroxidase activity was demonstrated by spectral and inhibition studies. Ascorbate could saturate TcAPX activity indicating that the enzyme obeys Michaelis-Menten kinetics. Parasites that overexpressed TcAPX activity were found to have increased resistance to exogenous H(2)O(2). To determine subcellular location an epitope-tagged form of TcAPX was expressed in T. cruzi, which was observed to colocalize with endoplasmic reticulum resident chaperone protein BiP. These findings identify an arm of the oxidative defense system of this medically important parasite. The absence of this redox pathway in the human host may be therapeutically exploitable.
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PMID:Trypanosoma cruzi expresses a plant-like ascorbate-dependent hemoperoxidase localized to the endoplasmic reticulum. 1235 82

The utility of plant secondary cell wall biomass for industrial and biofuel purposes depends upon improving cellulose amount, availability and extractability. The possibility of engineering such biomass requires much more knowledge of the genes and proteins involved in the synthesis, modification and assembly of cellulose, lignin and xylans. Proteomic data are essential to aid gene annotation and understanding of polymer biosynthesis. Comparative proteomes were determined for secondary walls of stem xylem and transgenic xylogenic cells of tobacco and detected peroxidase, cellulase, chitinase, pectinesterase and a number of defence/cell death related proteins, but not marker proteins of primary walls such as xyloglucan endotransglycosidase and expansins. Only the corresponding detergent soluble proteome of secretory microsomes from the xylogenic cultured cells, subjected to ion-exchange chromatography, could be determined accurately since, xylem-specific membrane yields were of poor quality from stem tissue. Among the 109 proteins analysed, many of the protein markers of the ER such as BiP, HSP70, calreticulin and calnexin were identified, together with some of the biosynthetic enzymes and associated polypeptides involved in polymer synthesis. However 53% of these endomembrane proteins failed identification despite the use of two different MS methods, leaving considerable possibilities for future identification of novel proteins involved in secondary wall polymer synthesis once full genomic data are available.
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PMID:The cell wall and secretory proteome of a tobacco cell line synthesising secondary wall. 1940 43