title: Effect of dietary zinc deficiency on protein synthesis in cell-free systems isolated from rat liver.
abstract: This study presents evidence for the direct involvement of zinc in the translation of polypeptide chains in rat liver. Cell-free systems consisting of polyribosomes and fractions, enriched with aminoacyl-tRNA synthetase for incorporation of amino acids into trichloroacetic acid-insoluble proteins, were prepared from livers of three populations of rats: 1) rats fed ad libitum a diet containing 25 ppm zinc; 2) rats fed a diet containing less than 1 ppm zinc; and 3) rats pair fed to the zinc-deficient group a diet containing 25 ppm zinc. Group 2 showed typical signs of zinc deficiency, including decreased bone zinc. The protein synthetic ability of systems isolated from zinc-deficient rats was considerably depressed, resulting in incorporation of 59-69% of the amino acids incorporated by systems from pair-fed rats and 54-59% of those incorporated by ad libitum-fed control animals. This effect was significant after only 14 d of the dietary regimen. Experiments performed by mixing polyribosomes and synthetase fractions from the different groups indicated that a defect is located in the synthetase fraction. Acylation of tRNA by the synthetase fraction also was assayed and found to be 69-90% of that in zinc-sufficient preparations. It is suggested that one or more of the aminoacyl-tRNA synthetase enzymes from the rat liver may be zinc dependent.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D000818:Animals; D002474:Cell-Free System; D004032:Diet; D008099:Liver / Q000378:metabolism*; D008297:Male; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors; D015032:Zinc / Q000008:administration & dosage / Q000172:deficiency*
chemical_list: D000596:Amino Acids; D000604:Amino Acyl-tRNA Synthetases; D015032:Zinc