CBP-140, a novel endoplasmic reticulum resident Ca(2+)-binding protein with a carboxy-terminal NDEL sequence showed partial homology with 70-kDa heat shock protein (hsp70).
Antibodies against pokeweed agglutinin binding proteins isolated from F9 embryonal carcinoma cells were used to screen a lambda gt11 expression library constructed from the cells. A cDNA clone thus obtained encoded a novel calcium binding protein of 140 kDa (CBP-140). Antibodies raised against the CBP-140 fusion protein stained a 140 kDa band in extracts not only from F9 cells but also from various mouse organs. A calcium blot experiment using CBP-140 fusion protein verified the calcium binding property of the protein. In the partial amino acid sequence so far clarified (652 amino acid residues) we could not detect EF-hand, but could detect contiguous acidic amino acids, which may serve as a calcium-binding site. CBP-140 showed homology with 70-kDa heat shock protein, though it was not induced by heat shock treatment. Localization of CBP-140 in endoplasmic reticulum was shown by indirect immunofluorescence staining and also by subcellular fractionation. Amino acid sequence of CBP-140 contains a carboxyl-terminal Asn-Asp-Glu-Leu (NDEL) sequence, which resembles Lys-Asp-Glu-Leu (KDEL) sequence, a signal to retain the resident proteins in endoplasmic reticulum; NDEL sequence may indeed play a similar role.
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Department of Biochemistry, Faculty of Medicine, Kagoshima University, Japan.
Ozawa
M
M
Yu
S
S
Miyauchi
T
T
Muramatsu
H
H
Muramatsu
T
T
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000302:isolation & purification*; D018236:Carcinoma, Embryonal / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins; D016415:Sequence Alignment
D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; D018840:HSP70 Heat-Shock Proteins; D011506:Proteins; C050087:oxygen-regulated proteins