JPDI, a novel endoplasmic reticulum-resident protein containing both a BiP-interacting J-domain and thioredoxin-like motifs.
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.
Mesh Terms:
3T3 Cells, Adenosine Triphosphatases, Adenosine Triphosphate, Amino Acid Motifs, Amino Acid Sequence, Animals, Blotting, Northern, Carrier Proteins, Endoplasmic Reticulum, Glutathione Transferase, HSP40 Heat-Shock Proteins, HeLa Cells, Heat-Shock Proteins, Humans, Hydrolysis, Mice, Microscopy, Fluorescence, Molecular Chaperones, Molecular Sequence Data, Protein Binding, Protein Biosynthesis, Protein Structure, Tertiary, Proteins, RNA, Messenger, Recombinant Fusion Proteins, Recombinant Proteins, Reverse Transcriptase Polymerase Chain Reaction, Sequence Homology, Amino Acid, Thioredoxins, Time Factors, Tissue Distribution
3T3 Cells, Adenosine Triphosphatases, Adenosine Triphosphate, Amino Acid Motifs, Amino Acid Sequence, Animals, Blotting, Northern, Carrier Proteins, Endoplasmic Reticulum, Glutathione Transferase, HSP40 Heat-Shock Proteins, HeLa Cells, Heat-Shock Proteins, Humans, Hydrolysis, Mice, Microscopy, Fluorescence, Molecular Chaperones, Molecular Sequence Data, Protein Binding, Protein Biosynthesis, Protein Structure, Tertiary, Proteins, RNA, Messenger, Recombinant Fusion Proteins, Recombinant Proteins, Reverse Transcriptase Polymerase Chain Reaction, Sequence Homology, Amino Acid, Thioredoxins, Time Factors, Tissue Distribution
J. Biol. Chem.
Date: Jan. 24, 2003
PubMed ID: 12446677
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