RAT-KIDNEY GLUTATHIONE-S-TRANSFERASE-1 SUBUNITS HAVE C-TERMINAL TRUNCATIONS

Cytosolic glutathione S-transferases (GSTs) from rat kidneys were puri fied by a combination of glutathione and S-hexyl-glutathione affinity columns. The isolated GSTs were subjected to reverse-phase HPLC and el ectrospray MS analysis. The major GST isoenzymes expressed in kidney a re subunits 1, 2, 7 and 8. GST 1', 3, and 4 are expressed in minor amo unts. GST 10 is barely detectable in the male kidney cytosol. The mole cular masses of these rat kidney GST subunits were determined by MS. T he values obtained for subunits 1', 2, 3, 4, 7, 8 and 10 are identical with those obtained for rat liver GSTs. Rat kidney GST 1 consists of three polypeptides, with molecular masses of 25517, 25372 and 24982 Da . Results from peptide mapping, MS and amino-acid-sequencing analyses indicate that the major components were generated by deleting the C-te rminal phenylalanine (24982 Da) and the C-terminal IFKF tetrapeptide ( 25372 Da) from the GST1 subunit, respectively. The 1-chloro-2,4-dinitr obenzene-conjugating and peroxidase activities of kidney GST 1 are sub stantially lower than for its counterpart from rat liver. In addition, rat kidney GST 1 has an arginine and a valine residue at positions 15 1 and 207 respectively. The results are in contradiction with the SWIS S-PROT and GenBank rat liver GST 1 cDNA-sequencing data, which give a lysine and a methionine at the corresponding positions. Further analys es indicate that rat liver GST 1 also has C-terminal phenylalanine del etion, and an arginine and a valine residue at positions 151 and 207 r espectively. However, the C-terminal-tetrapeptide-deleted form was not observed for rat liver GST 1.