J. Biol. Chem., Vol. 263, Issue 33, 17405-17411, Nov, 1988
Glutathione transferase from bovine placenta. Preparation, biochemical characterization, crystallization, and preliminary crystallographic analysis of a neutral class PI enzyme
J Schaffer, O Gallay and R Ladenstein
Max-Planck-Institut fur Biochemie, Martinsried, West Germany.
A method was developed to purify glutathione transferase from bovine
placenta by affinity chromatography and fast protein liquid chromatography.
The purified enzyme was homogeneous as judged by sodium dodecyl sulfate gel
electrophoresis and isoelectric focusing. The dimeric enzyme is composed of
identical subunits with a molecular weight of 23,000; its isoelectric point
is 6.9. In contrast to previously described isoenzymes of glutathione
transferase, the protein we have purified exists in two forms, an active
reduced form and a less active oxidized form. These can be reversibly
transformed into each other but behave differently in sedimentation
analysis, gel chromatography, and gel electrophoresis. These differences
may reflect a change in the molecular shape of glutathione transferase.
Chemical modification with iodoacetate, iodoacetamide (presumably of thiol
groups), phenylglyoxal, and butadione (presumably of arginyl groups), and
their inhibitory effects on the activity were investigated. From substrate
specificity studies and N-terminal sequence analysis it is obvious that
this glutathione transferase must belong to the isoenzyme class pi. The
purified enzyme could be crystallized from 1.4 M ammonium sulfate solution,
pH 8.0, in the presence of S-hexyl-glutathione. The crystals are
tetragonal, with space group P4(1)2(1)2 or P4(3)2(1)2. The cell constants
are a = b = 6.1 nm, c = 23.7 nm, alpha = beta = gamma = 90 degrees. The
crystals diffract to 0.26-nm resolution and are suitable for x-ray
structure analysis.