[Study of the quaternary structure of glutamate carboxylase from Escherichia coli].
It was shown by electron microscopy, that the native molecule of glutamate decarboxylase is a hexamer with dihedral symmetry; the subunits are situated at the apices of an octahedron. Apoenzyme at pH 6.0 is dissociated form. It were found s20.w - 12.8 +/- 0.54S and 5.51 +/- 0.43S for the native hexamer and a dissociated form, respectively. By column gel-filtration the molecular mass of the dissociated form was estimated as 105-106 kDa, this value corresponds to a dimer. There were 10 buried SH-groups per subunit in the hexamer, after dimer formation 8 of them became accessible. The reversible hexamer-dimer dissociation depends on pH and PLP. The pH dependences of the enzyme dissociation and activity are very similar. In the result of adding of 6 PLP equivalents to the dimers the reactivation and hexamer assembly were reached, the SH-groups burying preceded both these reactions. Effect of pH and PLP on the quaternary structure is known for some other PLP-enzymes. It may be the additional proof for the idea of a common ancestor for PLP-enzymes.
Sukhareva
B S
BS
Tikhonenko
A S
AS
Dariĭ
E L
EL
D002850:Chromatography, Gel; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D005969:Glutamate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008970:Molecular Weight
D046911:Macromolecular Substances; D005969:Glutamate Dehydrogenase
Issledovanie chetvertichnoĭ struktury glutamatdekarboksilazy iz Escherichia coli.