title: [Titration curves (ph gradient electrophoresis) of SHV-1 and SHV-2 beta-lactamases and a new type].
abstract: The molecular structures of the SHV-1 (p 453) and SHV-2 (pBP 60-1) beta-lactamases and of a new enzyme, a SHV-2 like extended broad-spectrum beta-lactamase (86-4), were compared by analysis of their titration curves (pH gradient electrophoresis). The titration curves of SHV-1 and SHV-2, which have the same isoelectric points (pI = 7.7). were completely superimposable for the whole of the pH gradient (pH 3.5-10), indicating a close homology between the two proteins, with perhaps the substitution of several amino acids by ones having the same charge. The curves of SHV-1 (pI = 7.7) and the new SHV-2-like enzyme (pI = 6.98) indicated that a basic residue in SHV-1 has been replaced by an acidic residue in the new SHV-2-like enzyme. These results show that, like SHV-2, the new beta-lactamase is a variant of SHV-1, and that the structural differences are probably limited to a very small number of amino acid residues. Nevertheless, this new beta-lactamase (SHV-3) may have arisen directly from SHV-1, indirectly via SHV-2, or even from another beta-lactamase.
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D009154:Mutation; D001618:beta-Lactamases / Q000032:analysis* / Q000145:classification / Q000235:genetics
chemical_list: D001618:beta-Lactamases
vernacular_title: Courbes de titration (électrophorèse en gradient de pH) des bêtalactamases SHV-1, SHV-2 et d'un nouveau type.