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)

In Saccharomyces cerevisiae Ydj1p, a DnaJ homolog, is localized to the cytosol with the Ssa and Ssb Hsp70 proteins. Ydj1p helps facilitate polypeptide translocation across mitochondrial and endoplasmic reticulum membranes (Caplan, A. J., Cyr, D. M., and Douglas, M. G. (1992) Cell 71, 1143-1155) and can directly interact with Ssa1p to regulate chaperone activity (Cyr, D. M., Lu, X., and Douglas, M. G. (1992) J. Biol. Chem. 267, 20927-20931). In this study, the role of Ydj1p in modulating ATP-dependent reactions catalyzed by Ssa and Ssb Hsp70 proteins has been examined using purified components and compared with that of other Hsp70 homologs BiP and DnaK. Ssa1p, Ssa2p, and Ssb1/2p all formed stable complexes with the mitochondrial presequence peptide, F1 beta(1-51). ATP alone had only modest effects on polypeptide complex formation with Ssa1p and Ssa2p, but prevented the majority of polypeptide binding to BiP and DnaK. ATP by itself also reduced polypeptide binding to Ssb1/2p to a level that was intermediate between that observed for the Ssa Hsp70 proteins tested and BiP and DnaK. ATP hydrolysis by Ssa1p, Ssa2p, and Ssb1/2p occurred at similar rates. Ydj1p was a potent modulator of the both the ATPase and polypeptide binding activities of Ssa1p and Ssa2p. In contrast, Ydj1p had little effect on the ATPase and polypeptide binding activity of Ssb1/2p. Therefore the chaperone-related activities of Ssa and Ssb Hsp70 proteins exhibit significant differences in sensitivity to ATP and YDJ1p. These data indicate that regulation of Hsp70 activity by DnaJ homologs can be specific. The specificity of interactions between Ydj1p and the Ssa and Ssb Hsp70 proteins observed could contribute in determining the functional specificity of these chaperones in the cytosol. In related experiments, F1 beta(1-51) was found to reduce the extent to which Ydj1p stimulated Ssa1p ATPase activity. This effect correlated with the formation of F1 beta(1-51).Ssa1p complexes. We propose that intramolecular communication between the polypeptide binding, ATPase and DnaJ regulatory domains on Ssa1p plays a role in the regulation of chaperone activity.
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PMID:Differential regulation of Hsp70 subfamilies by the eukaryotic DnaJ homologue YDJ1. 814 72

The immunoglobulin kappa light chain produced by the CH12 lymphoma is unusual because it is not secreted when expressed in the absence of a heavy chain. Instead, it undergoes rapid intracellular degradation. This degradation is selective, as another light chain expressed in the same cell is not degraded. It is also a property of the CH12 kappa chain itself, since it is degraded rapidly when expressed either in another myeloma cell or in COS-1 fibroblasts. When provided a heavy chain, this kappa chain assembles into IgM and is then protected from proteolysis. The degradation of kappa requires ATP, is sensitive to reduced temperature and to the thiol reagent diamide. Of all the proteolytic inhibitors tested, 3,4-dichloroisocoumarin, L-1-tosylamido-2-phenylethyl chloromethyl ketone, and to a lesser extent 1-chloro-3-tosylamido-7-amino-2-heptanone, inhibit kappa degradation, suggesting the involvement of a serine protease. The degradation of kappa does not require transport to the Golgi complex, nor is it sensitive to a variety of lysosomotropic agents. Both immunofluorescence and the observed association with the endoplasmic reticulum (ER) stress proteins GRP78/BiP and GRP94 indicate that the kappa chain is localized mostly in the ER. When a point mutation which blocks transport to the Golgi complex is introduced into this kappa chain, the association with the stress proteins is enhanced but the rate of degradation is not significantly decreased. We conclude that the CH12 kappa chain is a particularly good substrate for an ER degradation machinery, and that its sensitivity to the protease(s) is governed by its state of assembly. This ER degradation provides a possible quality control mechanism during the differentiation of B lymphocytes.
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PMID:Rapid degradation of an unassembled immunoglobulin light chain is mediated by a serine protease and occurs in a pre-Golgi compartment. 824 27

Reconstituted proteoliposomes derived from solubilized yeast microsomes are able to translocate a secreted yeast mating pheromone precursor (Brodsky, J. L., S. Hamamoto, D. Feldheim, and R. Schekman. 1993. J. Cell Biol. 120:95-107). Reconstituted proteoliposomes prepared from strains with mutations in the SEC63 or KAR2 genes are defective for translocation; the kar2 defect can be overcome by the addition of purified BiP (encoded by the KAR2 gene). We now show that addition of BiP to wild-type reconstituted vesicles increases their translocation efficiency three-fold. To identify other ER components that are required for translocation, we purified a microsomal membrane protein complex that contains Sec63p. We found that the complex also includes BiP, Sec66p (gp31.5), and Sec67p (p23). The Sec63p complex restores translocation activity to reconstituted vesicles that are prepared from a sec63-1 strain, or from cells in which the SEC66 or SEC67 genes are disrupted. BiP dissociates from the complex when the purification is performed in the presence of ATP gamma S or when the starting membranes are from yeast containing the sec63-1 mutation. We conclude that the purified Sec63p complex is active and required for protein translocation, and that the association of BiP with the complex may be regulated in vivo.
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PMID:A Sec63p-BiP complex from yeast is required for protein translocation in a reconstituted proteoliposome. 825 36

The major proteins in the lumen of the endoplasmic reticulum (ER) are thought to function in Ca2+ sequestration or as "molecular chaperones" in the folding and assembly of membrane or secreted proteins. Based on the ability of many chaperones to bind selectively to unfolded proteins and to dissociate from them upon ATP hydrolysis, we developed an affinity chromatography method to isolate proteins with these characteristics from pancreatic or liver ER. Seven ER proteins bound selectively to denatured protein columns and were specifically eluted by ATP (10(-6) M) but not by a nonhydrolyzable ATP analog. These proteins were identified with antibodies and microsequencing as the ER chaperone BiP (grp78), grp94, calreticulin, a novel 46-kDa protein that binds azido-ATP, as well as three members of the thioredoxin superfamily: protein-disulfide isomerase, ERp72, and a previously reported 50-kDa protein (p50). This set of seven proteins bound to and was eluted with ATP from a variety of denatured proteins, including histone, gelatin, alpha fetoprotein, thyroglobulin, lysozyme, casein, and IgG. The release of grp94, protein-disulfide isomerase, ERp72, calreticulin, and p50 was stimulated by Ca2+ in the presence of ATP. These proteins thus appear to function as Ca(2+)-dependent chaperones, which may account for the Ca2+ and ATP requirement for protein folding in the ER.
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PMID:A set of endoplasmic reticulum proteins possessing properties of molecular chaperones includes Ca(2+)-binding proteins and members of the thioredoxin superfamily. 829 23

Nascent proteins destined to be processed to a glycosylphosphatidylinositol (GPI)-anchored membrane form contain NH2-terminal and COOH-terminal signal peptides. The first directs a nascent protein into the endoplasmic reticulum; the second peptide targets the protein to a putative COOH-terminal signal transamidase where cleavage of the peptide and addition of the GPI anchor occur. We recently showed that ATP hydrolysis is required for maturation of GPI proteins at a stage prior to transamidation. Here we show that one of the ATP-requiring proteins involved in processing of GPI-anchored proteins in the endoplasmic reticulum is the immunoglobulin heavy chain binding protein (BiP; GRP 78). This and related findings indicate that GPI transamidase is localized in the endoplasmic reticulum.
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PMID:Evidence that the putative COOH-terminal signal transamidase involved in glycosylphosphatidylinositol protein synthesis is present in the endoplasmic reticulum. 838 4

We reconstituted prepro-alpha-factor translocation and signal peptide processing using a yeast microsomal detergent soluble fraction formed into vesicles with soybean phospholipids. Reconstituted translocation required ATP, and was deficient when sec63 and kar2 (BiP) mutant cells were used as a source of membranes. Normal translocation was observed with vesicles reconstituted from a mixture of pure wild-type yeast BiP and a soluble fraction of kar2 mutant membranes. Two other heat-shock cognate (hsc) 70 homologs, yeast cytosolic hsc70 (Ssalp) and E. coli dnaK protein did not replace BiP. Conversely, BiP was not active under conditions where translocation into native ER vesicles required cytosolic hsc70. We conclude that cytosolic hsc70 and BiP serve noninterchangeable roles in polypeptide translocation, possibly because distinct, asymmetrically oriented membrane proteins are required to recruit each protein to opposing surfaces of the ER membrane.
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PMID:Reconstitution of protein translocation from solubilized yeast membranes reveals topologically distinct roles for BiP and cytosolic Hsc70. 841 98

The 90-kDa heat shock protein (hsp90) is a well conserved, abundant cytosolic protein believed to be a "chaperone" of most steroid receptors. We have recently demonstrated that hsp90 has an ATP-binding site and autophosphorylating activity (Csermely, P., and Kahn, C. R. (1991) J. Biol. Chem. 266, 4943-4950). Circular dichroism analysis of highly purified hsp90 from rat liver shows that ATP induces an increase of beta-pleated sheet content of hsp90. Vanadate, molybdate, and heat treatment at 56 degrees C induce a similar change in the circular dichroism spectrum. Fourier transformed infrared spectroscopy reveals an ATP-induced increase in the interchain interactions of the 90-kDa heat shock protein due to an increase in its beta-pleated sheet content. In further studies we found that ATP: 1) decreases the tryptophan fluorescence of hsp90 by 11.6 +/- 1.9%; 2) increases the hydrophobic character of the protein as determined by its distribution between an aqueous phase and phenyl-Sepharose; and 3) renders hsp90 less susceptible to tryptic digestion. Our results suggest that hsp90 undergoes an "open-->closed" conformational change after the addition of ATP, analogous in many respects to the similar changes of the DnaK protein, the immunoglobulin heavy chain binding protein (BiP/GRP78), and hsp70. The ATP-induced conformational change of hsp90 may be important in regulating its association with steroid receptors and other cellular proteins.
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PMID:ATP induces a conformational change of the 90-kDa heat shock protein (hsp90). 842 Sep 64

The transfer of precursor proteins through the membrane of the rough endoplasmic reticulum (ER) in yeast is strictly dependent on the presence of ATP. Since Kar2p (the yeast homologue of mammalian BiP) is required for translocation, and is an ATP binding protein, an ATP transport system must be coupled to the translocation machinery of the ER. We report here the characterization of a transport system for ATP in vesicles derived from yeast ER. ATP uptake into vesicles was found to be saturable in the micromolar range with a Km of 1 x 10(-5) M. ATP transport into ER vesicles was specifically inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), a stilbene derivative known to inhibit a number of other anion transporters, and by 3'-O-(4-benzoyl)benzoyl-ATP (Bz2-ATP). Inhibition of ATP uptake into yeast microsomes by DIDS and Bz2-ATP blocked protein translocation in vitro measured co- as well as post-translationally. The inhibitory effect of DIDS on translocation was prevented by coincubation with ATP. Moreover, selective membrane permeabilization, allowing ATP access to the lumen, restored translocation activity to DIDS-treated membranes. These results demonstrate that translocation requires a DIDS and Bz2-ATP-sensitive component whose function is to transport ATP to the lumen of the ER. These findings are consistent with current models of protein translocation in yeast which stipulate the participation of Kar2p in the translocation process.
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PMID:An ATP transporter is required for protein translocation into the yeast endoplasmic reticulum. 844 Feb 56

Transport of presecretory proteins into mammalian microsomes involves a microsomal protein which is sensitive to photoaffinity labeling with 8-azido-ATP. Typically, protein folding within the lumen of the endoplasmic reticulum of mammalian cells depends on ATP and the member of the Hsp70 protein family, BiP. Here we addressed the question of whether protein transport into and folding within microsomes are differentially affected by photoaffinity labeling of microsomes with 8-azido-ATP. Folding of heterodimeric luciferase to the native state was more azido-ATP-sensitive compared to transport of the precursors of the two subunits. Therefore, we conclude that the microsomal protein which is responsible for the ATP-dependence of protein folding in the endoplasmic reticulum is sensitive to photoaffinity labeling with 8-azido-ATP and that this microsomal protein is distinct from the microsomal ATP-binding protein which is involved in protein transport.
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PMID:Protein folding within and protein transport into mammalian microsomes are differentially affected by photoaffinity labeling of microsomes with 8-azido-ATP. 856 77

A group of resident ER proteins have been identified that are proposed to function as molecular chaperones. The best characterized of these is BiP/GRP78, an hsp70 homologue that binds peptides containing hydrophobic residues in vitro and unfolded or unassembled proteins in vivo. However, evidence that mammalian BiP plays a direct role in protein folding remains circumstantial. In this study, we examine how BiP interacts with a particular substrate, immunoglobulin light chain (lambda LC), during its folding. Wild-type hamster BiP and several well-characterized BiP ATPase mutants were used in transient expression experiments. We demonstrate that wild-type lambda LCs showed prolonged association with mutant BiP which inhibited their secretion. Both wild-type and mutant BiP bound only to unfolded and partially folded LCs. The wild-type BiP was released from the incompletely folded LCs, allowing them to fold and be secreted, whereas the mutant BiP was not released. As a result, the LCs that were bound to BiP mutants were unable to undergo complete disulfide bond formation and were retained in the ER. Our experiments suggest that LCs undergo both BiP-dependent and BiP-independent folding steps, demonstrating that both ATP binding and hydrolysis activities of BiP are essential for the completion of LC folding in vivo and reveal that BiP must release before disulfide bond formation can occur in that domain.
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PMID:Inhibition of immunoglobulin folding and secretion by dominant negative BiP ATPase mutants. 864 65


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