Cell-free translation of mouse liver mRNA coding for two forms of UDP glucuronosyltransferase

Mouse liver poly(A) RNA, when translated in vitro, produced two forms of UDP glucuronosyltransferase with molecular weights of approximately 50,000 and 54,000 (designated GT_m1 and GT_m2, respectively). These forms were identified by antibody prepared against GT_m1. The mRNA coding for GT_m1 was preferentially increased twofold after treatment of mice with 3-methylcholanthrene, while GT_m2 mRNA was unaffected. Phenobarbital, however, increased the translatable levels of the mRNAs coding for both proteins approximately twofold. GT_m1 was shown to be glycosylated during translation in the presence of dog pancreatic microsomes. This was reflected by a decrease in mobility of the protein in sodium dodecyl sulfate-polyacrylamide gels as compared to GT_m1 translated in the absence of microsomes. Further evidence for glycosylation in vivo was demonstrated by an increase in the mobility of GT_m1 immunoadsorbed from microsomes treated with endoglycosidase H. In contrast, GT_m2 was unmodified. This apparent difference in the state of glycosylation may reflect a difference in the transmembrane distribution of these two enzyme forms, and hence play an important role in determining the type of aglycone glucuronidated and its route of removal from the cell.