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)

A hybrid protein consisting of the Escherichia coli lipoprotein signal sequence attached to the mature sequence of the B subunit of heat-labile enterotoxin (Lipo-EtxB) was expressed in yeast and E. coli. Analyses of cell lysates from Saccharomyces cerevisiae and E. coli expressing the protein revealed that both organisms were able to assemble Lipo-EtxB into oligomers that were (i) stable in the presence of sodium dodecyl sulphate, (ii) resistant to proteinase K degradation, and (iii) able to bind to GM1-ganglioside receptors. Each of these properties are characteristic of the wild-type B subunit pentamer produced in E. coli. Assembly of Lipo-EtxB was found to be unaffected in a sec18 mutant of S. cerevisiae, which possesses a temperature-sensitive defect in protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus, but was found not to assemble in a sec53 mutant, which causes the misfolding of proteins targeted to the ER. A kar2-1 mutation with a defect in the yeast homologue of BiP caused an 18-fold reduction in Lipo-EtxB assembly at the non-permissive temperature in S. cerevisiae. However, introduction of the wild-type KAR2 gene on a plasmid into the kar2-1 mutant completely suppressed the inhibition of Lipo-EtxB assembly. This provides the first evidence that KAR2 facilitates the assembly of an oligomeric protein in yeast and thus implicates KAR2 as a 'molecular chaperone'. The possible mechanisms of enterotoxoid assembly in E. coli and S. cerevisiae are discussed.
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PMID:Targeting and assembly of an oligomeric bacterial enterotoxoid in the endoplasmic reticulum of Saccharomyces cerevisiae. 177 57

Acetyl-CoA carboxylase (ACC1) catalyzes the first and rate limiting step of de novo fatty acid synthesis. Defects in Acc1p were recently correlated with an altered structure/function of the nuclear envelope in yeast. The subcellular distribution of the enzyme was determined in wild-type and mutant cells by cell fractionation and confocal immunofluorescence microscopy. Even though fatty acid synthesis is generally considered to be a cytosolic reaction, we found that Acc1p cofractionated with nuclei and the ER (endoplasmic reticulum) marker BiP/Kar2p. Membrane-bound Acc1p was susceptible to proteinase K digestion and was solubilized by mild salt treatment indicating that it is loosely associated with the cytosolic surface of the nuclear ER membrane. Consistent with these observations, immunofluorescence analysis revealed that Acc1p was distributed in a gradient within the cytoplasm that had its highest concentration around the ER. Possible association of Acc1p with the nuclear pore complexes (NPCs) was investigated in strains that display NPC clustering. Results of these experiments suggest that Acc1p localization is independent of NPC distribution. We propose that association of Acc1p with the cytoplasmic surface of the ER membrane is physiologically relevant to "channel" the enzymatic product of Acc1p, malonyl-CoA, to a putative ER-localized fatty acid chain elongase complex.
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PMID:Yeast acetyl-CoA carboxylase is associated with the cytoplasmic surface of the endoplasmic reticulum. 943 37

We have investigated recombinant fibrillin-1 (profib-1) and fibrillin-2 (glyfib-2) molecules encoding the proline- or glycine-rich regions with flanking domains (exons 9-11), in order to establish whether these sequences might mediate specific molecular recognition events important in fibrillin assembly. Our data demonstrate that both recombinant molecules can form extracellular dimers, but highlight subtle differences in the stability of these dimers. Following expression in COS-1 cells, SDS-PAGE analysis showed that glyfib-2 was present intracellularly as monomers, and extracellularly as monomers and disulphide-bonded dimers. Size fractionation in native non-reducing conditions prior to SDS-PAGE analysis highlighted that glyfib-2 also formed non-covalent associations. In contrast, profib-1 appeared monomeric in cells and medium. Using an in vitro translation system supplemented with semipermeabilised HT1080 cells together with chemical crosslinking, dimers of the fibrillin-1 and fibrillin-2 molecules were detected. Dimerisation was not cell-dependent since molecules translated in the absence of cells dimerised, and was not an intracellular event as judged by proteinase K digestions. A crosslinking and coimmunoprecipitation strategy provided a means of investigating whether molecular chaperones might be involved in preventing dimerisation of translocated molecules. Proteinase K-resistant recombinant molecules associated rapidly with BiP, and thereafter with protein disulphide isomerase and calreticulin. Differences between the two fibrillin isoforms in ability to form stable dimers prompted investigation of the proline- and glycine-rich sequences. Differences in solubility and pI were apparent that may contribute to reduced stability of proline-rich region interactions. These studies suggest that extracellular dimer formation mediated by interactions of the proline- and glycine-rich regions may be a crucial early step in the extracellular assembly of fibrillin into microfibrils.
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PMID:Fibrillin assembly: dimer formation mediated by amino-terminal sequences. 1050 3

Recent studies have indicated that PrP23-98, an N-terminal portion of PrP, polymerizes into amyloid-like and proteinase K (PK)-resistant aggregates in the presence of NADPH with copper ions [19], and then that CRT suppressed aggregation of PrP23-98 and also promoted solubilization of the aggregates [18]. As it is interesting to find out whether other chaperones can inhibit aggregation of PrP23-98 in vitro similar to CRT, this study was conducted to determine whether BiP, Grp94, PDI Grp58 and heat shock cognate protein70 (Hsc70) can inhibit aggregation of PrP23-98 in vitro. The present results indicated that Grp94 suppressed aggregation of PrP23-98, but that Grp94 could not mediate solubilization occurred in the aggregates in contrast to CRT. Other chaperons induced aggregation of PrP23-98 in the absence of NADPH.
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PMID:Effect of Chaperones on Prion Protein PrP23-98 Aggregation In Vitro. 2763 55