Incorporation of retinoic acid into proteins via retinoyl-CoA.

The incorporation of tritiated retinoic acid into proteins has been studied in cell-free extracts from rat liver and kidney. Incubation with retinoic acid in the presence of ATP and CoA resulted in a CoA intermediate. This CoA intermediate is a substrate for enzymes that incorporate the labeled retinoic acid moiety into proteins (Mr = 14,000-60,000) as detected with SDS-polyacrylamide gel electrophoresis. In the microsomal fraction, the label was found in a single protein (Mr 30,000). Retinoic acid is linked to the protein via a thioester bond as indicated by neutral hydrolysis with hydroxylamine and the bond's sensitivity to reducing agent. The incorporation of labeled retinoic acid into the protein is very rapid but decreases upon prolonged incubation, suggesting a high turnover of retinoic acid in the protein.