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)

Active oxygens have been suggested to be involved in age-related alterations of organelles and molecules. In this study we investigated the influence of active oxygen on aminoacyl-tRNA synthetases partially purified from rat liver. Treatment of leucyl-tRNA synthetase with Fe3(+)-ascorbate resulted in the increased heat-lability of the enzyme. The inactivation was inhibited by radical scavengers such as mannitol and benzoate, suggesting that hydroxyl radicals are responsible for heat-labilization of the enzyme. On the other hand, a considerable part of tyrosyl-tRNA synthetase was converted to heat-labile forms without added iron and ascorbate under aerobic conditions but not under anaerobic conditions. These and other findings suggested that the heat-labilization of this enzyme is caused by active oxygens probably generated by the reaction of dioxygen and transition metal ions present in the enzyme preparations. Heat-inactivation curves of the enzymes modified as described above were similar to those observed for the enzymes from aged animals in that these enzymes exhibited higher percentages of heat-labile forms than the unmodified enzymes from young animals [Takahashi and Goto, 1987, Arch. Gerontol. Geriatr. 6, 73-82; Takahashi and Goto, 1987, Arch. Biochem. Biophys. 257, 200-206]. The present findings are consistent with the theory that active oxygens are involved in the age-related alterations of enzymes.
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PMID:Alteration of aminoacyl-tRNA synthetase with age: heat-labilization of the enzyme by oxidative damage. 231 Jan 91

Analysis of bovine respiratory isolates of Pasteurella multocida demonstrated that six of nine strains tested were capable of growth dependent upon bovine transferrin and of specifically binding ruminant transferrins. A single 82-kDa protein was affinity isolated from the P. multocida strains with immobilized bovine transferrin. In contrast to what has been observed in other species, binding of this protein to immobilized transferrin was specifically blocked by the N-lobe subfragment of bovine transferrin. A single gene encoding the 82-kDa protein was flanked by a leucyl-tRNA synthetase gene and an IS1060 element, in contrast to other species where genes encoding the two receptor proteins (TbpB and TbpA) are found in an operonic arrangement. A similar gene arrangement was observed in all of the receptor-positive strains, in spite of the observation that they belonged to different genomic groups. Analysis of the deduced amino acid sequence of the receptor protein indicated that it is a member of the TonB-dependent outer membrane receptor family, and although it is related to transferrin and lactoferrin receptor proteins (TbpAs and LbpAs) from other species, it differs substantially from other members of this group. Amino acid alignments suggest that the reduced size (20 kDa smaller) of the P. multocida TbpA is primarily due to the absence of larger predicted external loops. Collectively these results suggest that P. multocida has a single, novel receptor protein (TbpA) that is capable of efficiently mediating iron acquisition from bovine transferrin without the involvement of a second receptor protein (TbpB).
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PMID:Characterization of a novel transferrin receptor in bovine strains of Pasteurella multocida. 1120 86