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

Protein transport into the mammalian endoplasmic reticulum depends on nucleoside triphosphates. Photoaffinity labelling of microsomes with azido-ATP prevents protein transport at the level of association of precursor proteins with the components of the transport machinery, Sec61alpha and TRAM proteins. The same phenotype of inactivation was observed after depleting a microsomal detergent extract of ATP-binding proteins by passage through ATP-agarose and subsequent reconstitution of the pass-through into proteoliposomes. Transport was restored by co-reconstitution of the ATP eluate. This eluate showed eight distinct bands in SDS gels. We identified five lumenal proteins (Grp170, Grp94, BiP/Grp78, calreticulin and protein disulfide isomerase), one membrane protein (ribophorin I) and two ribosomal proteins (L4 and L5). In addition to BiP (Grp78), Grp170 was most efficiently retained on ATP-agarose. Purified BiP did not stimulate transport activity. Sequence analysis revealed a striking similarity of Grp170 and the yeast microsomal protein Lhs1p which was recently shown to be involved in protein transport into yeast microsomes. We suggest that Grp170 mediates efficient insertion of polypeptides into the microsomal membrane at the expense of nucleoside triphosphates.
 ...
PMID:A microsomal ATP-binding protein involved in efficient protein transport into the mammalian endoplasmic reticulum. 900 69

Secretion of newly synthesized proteins across the mammalian rough endoplasmic reticulum (translocation) is supported by the membrane proteins Sec61p and TRAM, but may also include accessory factors, depending on the particular translocation substrate. Studies designed to investigate the binding of anti-peptide antibodies to the carboxyl terminus of the alpha-subunit of Sec61 (Sec61palpha) lead us to the isolation of a complex of proteins that occlude the cytosolic face of Sec61palpha in microsomes that have been prepared by standard protocols used to study translocation in vitro [Walter, P., and Blobel, G. (1983) Methods Enzymol. 96, 84-93]. This complex was shown by nanospray tandem mass spectrometry to be composed of protein disulfide isomerase (PDI), calcium binding protein 1 (CABP1/P5), 72 kDa endoplasmic reticulum protein (ERp72), and BiP (heat shock protein A5/HSPA5), and has been named TR-PDI for "translocon-resident protein disulfide isomerase complex". This constitutes a novel location for these proteins, which are known to be major constituents of the lumen of the rough endoplasmic reticulum. We have not established the function of TR-PDI at this location, but did observe that the absence of this complex results in a relative loss of correct topology of prion protein insertion across RER membranes, indicating the possibility of a functional role in vivo.
 ...
PMID:A complex of chaperones and disulfide isomerases occludes the cytosolic face of the translocation protein Sec61p and affects translocation of the prion protein. 1459 96