Cloning and expression of a cDNA encoding human sterol carrier protein 2.
We report the cloning and expression of a cDNA encoding human sterol carrier protein 2 (SCP2). The 1.3-kilobase (kb) cDNA contains an open reading frame which encompasses a 143-amino acid sequence which is 89% identical to the rat SCP2 amino acid sequence. The deduced amino acid sequence of the polypeptide reveals a 20-residue amino-terminal leader sequence in front of the mature polypeptide, which contains a carboxyl-terminal tripeptide (Ala-Lys-Leu) related to the peroxisome targeting sequence. The expressed cDNA in COS-7 cells yields a 15.3-kDa polypeptide and increased amounts of a 13.2-kDa polypeptide, both reacting with a specific rabbit antiserum to rat liver SCP2. The cDNA insert hybridizes with 3.2- and 1.8-kb mRNA species in human liver poly(A)+ RNA. In human fibroblasts and placenta the 1.8-kb mRNA was most abundant. Southern blot analysis suggests either that there are multiple copies of the SCP2 gene in the human genome or that the SCP2 gene is very large. Coexpression of the SCP2 cDNA with expression vectors for cholesterol side-chain cleavage enzyme and adrenodoxin resulted in a 2.5-fold enhancement of progestin synthesis over that obtained with expression of the steroidogenic enzyme system alone. These findings are concordant with the notion that SCP2 plays a role in regulating steroidogenesis, among other possible functions.
Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia 19104.
R
R
Yamamoto
C B
CB
Kallen
G O
GO
Babalola
H
H
Rennert
J T
JT
Billheimer
J F
JF
Strauss
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics* / Q000302:isolation & purification; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D015723:Gene Library; D005822:Genetic Vectors; D006801:Humans; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger; D011994:Recombinant Proteins / Q000302:isolation & purification; D013256:Steroids / Q000096:biosynthesis; D013261:Sterols / Q000378:metabolism; D014162:Transfection
D002352:Carrier Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013256:Steroids; D013261:Sterols; C072087:sterol carrier proteins; D011061:Poly A; D012313:RNA; D004247:DNA