title: Purification and some properties of the histidyl-tRNA synthetase from the cytosol of rabbit reticulocytes.
abstract: The histidyl-tRNA synthetase of rabbit reticulocyte cytosol has been purified 84 000-fold to apparent homogeneity with a specific activity of 687 nmol of histidyl-tRNA formed per min per mg of protein. Ten to 15% of the enzyme activity is sedimented with the ribosomes while the remainder is in the cytosol. The purified enzyme has a molecular weight of 122 000 as determined by sucrose density gradient centrifugation. Gel electrophoresis in the presence of 0.1% sodium dodecyl sulfate suggests that it is composed of two similar subunits with a molecular weight of approximately 64 000. The enzyme has a magnesium optimum of 45 mM; however, this is reduced to 5 mM in the presence of an intracellular potassium concentration (160 nM). The enzyme acylates the two histidine tRNA isoacceptors of rabbit reticulocytes with similar Km values and at similar rates.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000302:isolation & purification*; D000818:Animals; D003600:Cytosol / Q000201:enzymology; D006643:Histidine-tRNA Ligase / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D010659:Phenylhydrazines / Q000494:pharmacology; D012346:RNA, Transfer, Amino Acyl / Q000096:biosynthesis; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology*
chemical_list: D046911:Macromolecular Substances; D010659:Phenylhydrazines; D012346:RNA, Transfer, Amino Acyl; D000604:Amino Acyl-tRNA Synthetases; D006643:Histidine-tRNA Ligase; D008274:Magnesium