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 Rab family of small GTPases is a subset of the Ras superfamily. Rabs regulate the flux through individual steps of the intracellular membrane trafficking pathway, such as ER-to-Golgi transport, probably by controlling SNARE complex assembly. In Trypanosoma brucei a number of Rab proteins have been isolated by EST analysis; here we characterise one of these, TbRab2p (originally designated Trab1p), which is a member of the Ypt1p subfamily of Rab proteins. Recombinant TbRab2p is capable of hydrolysing GTP and is post-translationally modified in vitro by addition of a geranylgeranyl prenyl group, properties of an authentic Rab GTPase. Antibodies against recombinant TbRab2p show that in trypanosomes TbRab2p is localised primarily to the endoplasmic reticulum (ER) and colocalises with BiP in wild-type trypanosomes. Over expression of TbRab2p in procyclic form T. brucei results in a cell population having a 40-fold increase in TbRab2p expression. In these cells biosynthesis of procyclin, a secretory pathway glycoprotein, is decreased, accompanied by an increase in general protein biosynthesis, suggesting that excess TbRab2p affects ER function. Heterologous expression of TbRab2p in COS cells resulted in targeting to the pre-Golgi transport intermediate (ERGIC), indicating that the targeting information is conserved between mammals and trypanosomes. Clustal and phylogenetic analyses support assignment of TbRab2p as a Rab2 homologue. In addition, over expression of TbRab2p in trypanosomes results in membrane reorganisation and formation of opaque vesicular structures visible by phase contrast microscopy, consistent with accumulation of ER-derived vesicular structures in cells highly overexpressing TbRab2p. Ultrastructural examination by electron microscopy confirmed the presence of a tubulo-vesicular membrane bound compartment in close proximity to the cis-Golgi, probably equivalent to the ERGIC. TbRab2p is therefore a new ER/ERGIC marker for T. brucei.
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PMID:TbRab2p, a marker for the endoplasmic reticulum of Trypanosoma brucei, localises to the ERGIC in mammalian cells. 985 68

Several endoplasmic reticulum (ER)-resident luminal proteins have a characteristic ER retrieval signal, KDEL, or its variants at their C terminus. Our previous work searching EST databases for proteins containing the C-terminal KDEL motif predicted some novel murine proteins, one of which designated JPDI (J-domain-containing protein disulfide isomerase-like protein) is characterized in this study. The primary structure of JPDI is unique, because in addition to a J-domain motif adjacent to the N-terminal translocation signal sequence, four thioredoxin-like motifs were found in a single polypeptide. As examined by Northern blotting, the expression of JPDI was essentially ubiquitous in tissues and almost independent of ER stress. A computational prediction that JPDI is an ER-resident luminal protein was experimentally supported by immunofluorescent staining of epitope-tagged JPDI-expressing cells together with glycosylation and protease protection studies of this protein. JPDI probably acts as a DnaJ-like partner of BiP, because a recombinant protein carrying the J-domain of JPDI associated with BiP in an ATP-dependent manner and enhanced its ATPase activity. We speculate that for the folding of some proteins in the ER, chaperoning by BiP and formation of proper disulfide bonds may synchronously occur in a JPDI-dependent manner.
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PMID:JPDI, a novel endoplasmic reticulum-resident protein containing both a BiP-interacting J-domain and thioredoxin-like motifs. 1244 77

We have previously identified in the human EST sequence data base four overlapping clones that could be aligned with both a predicted protein sequence, deduced from the C. elegans genomic sequence, and partial amino acid sequences, obtained for a protein from canine pancreatic microsomes. We suggested that these proteins are homologs of yeast microsomal and DnaJ-like protein Scj1p and termed them ERj3p. Here we verified the predicted protein sequence of human ERj3p by sequence analysis of the corresponding cDNA. Multiple alignment of related sequences identified these proteins as true homologs of yeast Scj1p. Biochemical analysis of the canine protein characterized ERj3p as a soluble glycoprotein of the pancreatic endoplasmic reticulum. This pancreatic DnaJ-like protein was shown to interact with lumenal DnaK-like proteins, such as BiP. Furthermore, we found that ERj3p interacts with SDF2L1 protein that may be involved in protein O-glycosylation. We propose that ERj3p represents a cochaperone of DnaK-like chaperones of the mammalian endoplasmic reticulum and is involved in folding and maturation of newly synthesized proteins.
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PMID:Characterization of pancreatic ERj3p, a homolog of yeast DnaJ-like protein Scj1p. 1519 98