Involvement of sterol carrier protein-2 in dolichol biosynthesis.
The effect of sterol carrier protein-2 (SCP-2) on dolichol biosynthesis by rat liver microsomes was investigated. cis-Prenyltransferase activity was stimulated 7-fold in the presence of 5 micrograms of purified SCP-2/mg of microsomal protein, which was similar to the increase obtained by adding detergent. The polyisoprenoid pattern obtained in the presence of SCP-2 was the same as that present in rat liver, in contrast to the pattern appearing upon incubation of microsomes with detergent, which gave shorter polyisoprenoids. Like SCP-2, the cytosolic fraction from rat liver also stimulated cis-prenyltransferase. Incubation with cytosol pretreated with anti-SCP-2 showed no stimulatory effect and led to the accumulation of shorter polyisoprenoids. SCP-2 had no appreciable effect on polyprenol alpha-saturase, dolichol kinase, dolichyl phosphate phosphatase, or acyl-CoA:dolichol acyltransferase. The results demonstrate that SCP-2 greatly stimulates and may regulate the condensation reactions mediated by cis-prenyltransferase in the process of dolichol biosynthesis and permits polymerization of the polyisoprenoid to its natural chain length.
Ericsson
J
J
Department of Biochemistry, University of Stockholm, Sweden.
Scallen
T J
TJ
Chojnacki
T
T
Dallner
G
G
D000418:Albumins / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001345:Autoradiography; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003574:Cytochrome c Group / Q000494:pharmacology; D004122:Dimethylallyltranstransferase / Q000378:metabolism; D004286:Dolichols / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D010940:Plant Proteins; D011107:Polylysine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013261:Sterols / Q000378:metabolism*; D013379:Substrate Specificity
D000418:Albumins; D000906:Antibodies; D002352:Carrier Proteins; D003574:Cytochrome c Group; D004286:Dolichols; D010940:Plant Proteins; D013261:Sterols; C072087:sterol carrier proteins; D011107:Polylysine; D004122:Dimethylallyltranstransferase