Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.1.1.4 (leucyl-tRNA synthetase)
 297 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present investigation was undertaken to clarify the effect of zinc on bone protein synthesis in tissue culture. Calvaria were removed from 3-week-old male rats and cultured for periods up to 96 hr in Dulbecco's Modified Eagle Medium (high glucose, 4500 mg/dl) supplemented with antibiotics and bovine serum albumin. The calvaria were incubated at 37 degrees in 5% CO2/95% air in the medium containing 10(-6)-10(-4) M zinc. Zinc content in bone cells was increased when the culture was treated with 10(-5) and 10(-4) M zinc for 48 hr. When calvaria cultured in the presence of 10(-4) M zinc were pulsed with [14C]uridine, the incorporation of [14C]uridine into the bone RNA was not increased significantly. In the pulse with [3H]leucine, the presence of 10(-5) to 10(-4) M zinc in the medium caused a significant increase in the incorporation of [3H]leucine into the acid-insoluble residues of bone tissue. This increase was blocked completely by treatment with 10(-7) M cycloheximide, an inhibitor of protein synthesis. When [3H]leucine was added into the reaction mixture containing the 5500 g supernatant fraction of the homogenate prepared from calvaria cultured in the presence of 10(-4) M zinc, the in vitro protein synthesis was increased about 2-fold. The activity of [3H]leucyl-tRNA synthetase in the 105,000 g supernatant fraction (cytosol) of the bone homogenate was increased about 2-fold by the culture with 10(-4) M zinc. The presence of 10(-4) M dipicolinate, a specific chelator of zinc, in the culture medium negated the effect of zinc on [3H]leucyl-tRNA synthetase activity. The addition of 10(-7) to 10(-6) M zinc into the reaction mixture containing enzyme extracts obtained from uncultured rat calvaria caused a 2-fold increase of [3H]leucyl-tRNA synthetase activity. These results clearly indicate that zinc induces the stimulation of protein synthesis at the translational level in bone cells. The present study further supports the view that zinc increases protein synthesis in bone cells and that the metal induces bone formation.
 ...
PMID:Zinc stimulation of bone protein synthesis in tissue culture. Activation of aminoacyl-tRNA synthetase. 246 Dec 1

The effect of inhibition of protein synthesis on the synthesis and processing of low molecular weight RNA (LMW RNA) hs been studied on CHO-tsH1, a mutant cell line in which protein synthesis is rapidly inhibited at non-permissive temperature by inactivation of the enzyme leucyl-tRNA synthetase. The increase in temperature results in an increase in uridine uptake and in the specific activity of UTP pool which is probably not related to the mutation. We report in this paper that there is no significant alteration in the synthesis of LMW RNA (including 5S ribosomal RNA (rRNA) and tRNA) except for the inhibition of synthesis of nucleolar RNA species A. Since, in a previous paper, it has been shown that the processing of preribosomal nucleolar RNA does not proceed at 39.5 degrees C in CHO-tsH1 cells, these results are consistent with the hypothesis that nucleolar RNA species A is involved in the processing of rRNA depends on its synthesis and maturation.
 ...
PMID:Effects of protein synthesis inhibition on low molecular weight RNA metabolism in tsH1, a mutant cell line with a temperature-sensitive leucyl-tRNA synthetase. 618 36

A number of yeasts of the genus Candida translate the standard leucine-CUG codon as serine. This unique genetic code change is the only known alteration to the universal genetic code in cytoplasmic mRNAs, of either eukaryotes or prokaryotes, which involves reassignment of a sense codon. Translation of CUG as serine in these species is mediated by a novel serine-tRNA (ser-tRNACAG), which uniquely has a guanosine at position 33, 5' to the anticodon, a position that is almost invariably occupied by a pyrimidine (uridine in general) in all other tRNAs. We propose that G-33 has two important functions: lowering the decoding efficiency of the ser-tRNACAG and preventing binding of the leucyl-tRNA synthetase. This implicates this nucleotide as a key player in the evolutionary reassignment of the CUG codon. In addition, the novel ser-tRNACAG has 1-methylguanosine (m1G-37) at position 37, 3' to the anticodon, which is characteristic of leucine, but not serine tRNAs. Remarkably, m1G-37 causes leucylation of the ser-tRNACAG both in vitro and in vivo, making the CUG codon an ambiguous codon: the polysemous codon. This indicates that some Candida species tolerate ambiguous decoding and suggests either that (i) the genetic code change has not yet been fully established and is evolving at different rates in different Candida species; or (ii) CUG ambiguity is advantageous and represents the final stage of the reassignment. We propose that such dual specificity indicates that reassignment of the CUG codon evolved through a mechanism that required codon ambiguity and that ambiguous decoding evolved to generate genetic diversity and allow for rapid adaptation to environmental challenges.
 ...
PMID:The non-standard genetic code of Candida spp.: an evolving genetic code or a novel mechanism for adaptation? 940 14