Y. Takahashi et al., A BASIS FOR DIFFERENTIATING AMONG THE MULTIPLE HUMAN MU-GLUTATHIONE S-TRANSFERASES AND MOLECULAR-CLONING OF BRAIN GSTM5, The Journal of biological chemistry, 268(12), 1993, pp. 8893-8898
Specific cDNA probes and antisera were employed to interpret genetic p
olymorphisms of human Mu-class glutathione S-transferases and to provi
de a basis for identifying individual forms in human tissues. A cDNA p
robe that cross-hybridized with various human and rodent Mu-glutathion
e S-transferase transcripts, hybridized with at least three discrete c
omponents by Northern analysis of RNA from human tissue. The smallest
(1.3 kb) transcript was identified as the one that encodes GSTM3-3 sub
units. A form designated GSTM5, was cloned from a human brain cDNA lib
rary and its sequence determined. The open reading frame of GSTM5 shar
ed a high degree of homology with the sequences of other Mu-class glut
athione S-transferases, but its 846-nucleotide 3'-noncoding region was
unique and considerably larger than that of any of the other Mu forms
. Specific synthetic peptide antigens were utilized to distinguish amo
ng Mu-class glutathione S-transferases in different tissues of represe
ntative individuals. The primary hepatic transcript was that encoding
GSTM1-1 with much lesser amounts of GSTM3-3, but livers were devoid of
GSTM2-2, and GSTM5-5. Immunoblots confirmed that null-phenotype indiv
iduals lacked the GSTM1 gene rather than its GSTM2 homologue that is n
early identical in its exon sequences. The null phenotype therefore wa
s conspicuous in liver, where GSTM1-1 ordinarily was the predominant M
u transcript, but brain and testis contained all four forms. A general
strategy was devised to distinguish among and assign primary structur
es to individual glutathione S-transferases from human tissue.