[Localization of human sterol carrier protein 2 gene and cDNA expression in COS-7 cell].

Sterol carrier protein 2 (SCP2) is known to be an important polypeptide in intracellular sterol and lipid movement. Here are reported the cloning and expression of a cDNA encoding human SCP2, and the assignment of SCP2 gene to human chromosome 1. The 1,229 bp cDNA contains an open reading frame and the encoded polypeptide consists of 143 amino acids. This polypeptide is very similar in amino acid composition to human, bovine and rat liver SCP2. The deduced amino acid sequence of this cDNA has a 20-residue amino-terminal leader sequence with mature SCP2. Northern blot analysis suggests that there are 1.8 kb and 3.2 kb mRNA species in human liver poly (A)+RNA. PCR analysis of human x rodent somatic cell hybrid panels indicates that the gene encoding SCP2 is on human chromosome 1. Transient expression of the human liver SCP2 cDNA in COS-7 cells shows a 15.3KDa polypeptide and increased amounts of a 13.2KDa polypeptide. Coexpression of the SCP2 cDNA with cholesterol side-chain cleavage enzyme and adrenodoxin cDNAs resulted in a 2.5-fold progestin synthesis in comparison with that of the steroidogenic enzyme system alone. These findings suggest that SCP2 plays a role in regulating steroidogenesis, among other possible functions.