Cab45, a novel (Ca2+)-binding protein localized to the Golgi lumen.
We have identified and characterized Cab45, a novel 45-kD protein from mouse 3T3-L1 adipocytes. Cab45 is ubiquitously expressed, contains an NH2-terminal signal sequence but no membrane-anchor sequences, and binds Ca2+ due to the presence of six EF-hand motifs. Within the superfamily of calcium-binding proteins, it belongs to a recently identified group of proteins consisting of Reticulocalbin (Ozawa, M., and T. Muramatsu. 1993. J. Biol. Chem. 268:699-705) and ERC 55 (Weis, K., G. Griffiths, and A.I. Lamond. 1994. J. Biol Chem. 269:19142-19150), both of which share significant sequence homology with Cab45 outside the EF-hand motifs. In contrast to reticulocalbin and ERC-55 which are soluble components of the endoplasmic reticulum, Cab45 is a soluble protein localized to the Golgi. Cab45 is the first calcium-binding protein localized to the lumenal portion of a post-ER compartment; Cab45 is also the first known soluble protein resident in the Golgi lumen. Cab45 can serve as a model protein to determine the mechanism of retention of soluble proteins in the Golgi compartment.
Scherer
P E
PE
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142-1479, USA.
Lederkremer
G Z
GZ
Williams
S
S
Fogliano
M
M
Baldini
G
G
Lodish
H F
HF
D016475:3T3 Cells; D017667:Adipocytes; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020126:Brefeldin A; D002135:Calcium-Binding Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D006023:Glycoproteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA
D002135:Calcium-Binding Proteins; D003517:Cyclopentanes; D018076:DNA, Complementary; D006023:Glycoproteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C099100:SDF4 protein, human; D020126:Brefeldin A