P. Zimniak et al., ESTIMATION OF GENOMIC COMPLEXITY, HETEROLOGOUS EXPRESSION, AND ENZYMATIC CHARACTERIZATION OF MOUSE GLUTATHIONE-S-TRANSFERASE MGSTA4-4 (GST-5.7), The Journal of biological chemistry, 269(2), 1994, pp. 992-1000
We have previously isolated a cDNA clone for a unique mouse lung gluta
thione S-transferase, mGSTA4-4 (GST 5.7) (Zimniak, P., Eckles, M. A.,
Saxena, M., and Awasthi, Y. C. (1992) FEBS Lett. 313,173-176). By geno
mic Southern blotting and polymerase chain reaction single strand conf
ormation polymorphism analysis we have now demonstrated the presence o
f at least two mGSTA4-related genes in the mouse. The heterogeneity of
mGSTA4-4 was further examined by comparing the structural and kinetic
properties of mGSTA4-4 isolated from mouse lung with those of recomhi
nant recmGSTA4-4 expressed in Escherichia coli. Except for the isoelec
tric point, the physical properties of the two proteins were indisting
uishable. Western blots using antibodies against rec-mGSTA4-4 have sho
wn selective expression of the enzyme in mouse tissues. Even though th
e substrate specificity profiles of the tissue-isolated and recombinan
t enzymes, which point to a role of mGSTA4-4 in the detoxification of
lipid peroxidation products, were generally similar, significant diffe
rences were observed with selected substrates. The existence of functi
onally distinct forms of mGSTA4-4 and the presence of more than one ge
ne strongly suggest that the previously observed differences in proper
ties of mGSTA4-4 isolated from various mouse tissues (Awasthi, S., Sin
ghal, S. S., Srivastava, S. K., and Awasthi, Y. C. (1993) Arch. Bioche
m. Biophys. 301, 143-150) may be due to tissue-specific expression of
mGSTA4-related genes.