title: Cysteinyl-tRNA synthetase from Bacillus stearothermophilus. A structural and functional monomer.
abstract: A procedure is described for the purification of cysteinyl-tRNA synthetase as a side product of a multi-enzyme isolation from Bacillus stearothermophilus. The native and denatured enzyme are both shown to have a molecular weight of 54000 by gel filtration and sodium dodecyl sulphate/polyacrylamide gel electrophoresis respectively. Fingerprinting and peptide counting indicate that the polypeptide chain has a nonrepeating primary structure. The enzyme has only one binding site for each of its substrates (cysteine, ATP and tRNACys) as judged by equilibrium dialysis, active-site titration and fluorescence quenching. No evidence for the dimerisation of the enzyme in the presence of these substrates could be found. We conclude that cysteinyl-tRNA synthetase, which is the smallest aminoacyl-tRNA synthetase yet described, is both structurally and functionally monomeric.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000604:Amino Acyl-tRNA Synthetases / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D003545:Cysteine; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D013050:Spectrometry, Fluorescence
chemical_list: D000596:Amino Acids; D000604:Amino Acyl-tRNA Synthetases; C019975:cysteinyl-tRNA synthetase; D003545:Cysteine