Partial purification, characterization and translation in vitro of rat liver metallothionein messenger ribonucleic acid.
Poly(A)+ (polyadenylated) mRNA coding for metallothioneins was purified 13-fold from rat liver polyribosomes and was identified by its ability to direct the biosynthesis of these proteins in a wheat-germ cell-free system. The carboxymethylated products of the protein-synthesizing system in vitro were analysed with sodium dodecyl sulphate/20% polyacrylamide-gel electrophoresis. The labelled compounds [3H]serine and [35S]cysteine were incorporated at high specific radioactivity into proteins that co-migrated with authentic metallothioneins. No [3H]leucine incorporation was found, in agreement with the amino acid composition of the metallothioneins. Metallothionein mRNA had a sedimentation coefficient of 9 S and carried a maximum of four ribosomes. At 5 h after a subcutaneous injection of ZnCl2 or CdCl2 (10 mumol/kg body wt.), the amount of this mRNA increased approx. 2- and 4-fold respectively, on the basis of translation in vitro. The increase in metallothionein mRNA (defined by translation in the wheat-germ system) was transient and, after CdCl2 treatment, fell back to control values by 17 h. Metallothioneins constituted a maximum of 0.8% of the total protein products synthesized in the wheat-germ system by total mRNA isolated from rat liver after CdCl2 treatment.
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000032:analysis* / Q000187:drug effects; D008667:Metalloproteins / Q000096:biosynthesis; D008668:Metallothionein / Q000096:biosynthesis; D011061:Poly A; D011132:Polyribosomes / Q000032:analysis / Q000187:drug effects; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification*; D051381:Rats; D015032:Zinc / Q000494:pharmacology
D008667:Metalloproteins; D012333:RNA, Messenger; D002104:Cadmium; D011061:Poly A; D008668:Metallothionein; D015032:Zinc