title: Disulfide bond engineered into T4 lysozyme: stabilization of the protein toward thermal inactivation.
abstract: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D004274:DNA, Recombinant / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D005818:Genetic Engineering; D007700:Kinetics; D009113:Muramidase / Q000235:genetics* / Q000378:metabolism; D011489:Protein Denaturation
chemical_list: D004274:DNA, Recombinant; D009113:Muramidase