Rat kidney glutathione S-transferase 1 subunits have C-terminal truncations

Purification and characterization of a novel glutathione S-transferase from Asaphis dichotoma

An isoenzyme of glutathione S-transferase (adGST) was purified from liver intestine of the seashell (Asaphis dichotoma) by GST-Sepharose 4B affinity chromatography followed by reverse-phase HPLC. The enzyme has a pI value of 4.6 and is composed of two subunits each with a molecular weight of 23kDa. It exhibits different catalytic activities toward the substrates 1-chloro-2,4-dinitrobenzene, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, ethacrynic acid, and p-nitrophenyl acetate and, fascinatingly, shows high activity toward CDNB. The amino acid composition of adGST was determined and found to be very similar to the Sloane squid GSTs. N-terminal analysis of the first 15 residues of adGST revealed that it has 73% sequence identity with the pig roundworm GSTs. The adGST shows characteristics similar to those of class sigma GSTs, as was indicated by its substrate specificity, N-terminal amino acid sequence, and amino acid composition.

Purification and characterization of multiple glutathione S-transferase isozymes from Chironomidae larvae

Glutathione S-transferase (GST) has been implicated in the process of biotransformation of polycyclic aromatic hydrocarbons and of other organic pollutants by Chironomidae larvae. We have purified and characterized GST from cytosolic fractions of Chironomidae larvae. GST with an M(r) of 23 kDa has been purified to homogeneity from larvae by centrifugation, size exclusion chromatography on Sephadex G25, and glutathione affinity and anion exchange chromatography. The purified enzyme exhibited moderate activity towards 1,2-dichloro-4-nitrobenzene, 1-chloro-2,4-dinitrobenzene, 4-nitropyridine-N-oxide, p-nitrobenzyl chloride, ethacrynic acid, and cumene hydroperoxide. The enzyme was homogeneous on gel isoelectric focusing and on SDS gel electrophoresis. Its isoelectric point was estimated to be 5.5. The enzyme had a maximum activity at approximately pH 8 and showed activity between 30 and 40 degrees C. It became inactive at higher temperature (>50 degrees C) for 5 min. The N-terminal sequence analysis of the amino acids shows a high % of conserved regions in the enzyme. The enzyme activity was comparable to levels of metabolism observed by animal GST involved in the detoxification of xenobiotics.

Characterization and cloning of avian-hepatic glutathione S-transferases

Cytosolic glutathione S-transferases (GSTs) were isolated from 1-day-old Leghorn chick livers by glutathione (GSH)-affinity chromatography. After sample loading and extensive washing with 0.2 M NaCl, the column was sequentially eluted with 5 mM GSH and 1 mM S-hexylglutathione. The isolated GSTs were subjected to reverse-phase HPLC, electrospray ionization-MS, N-terminal and internal peptide sequencing analyses. The proteins recovered from the 5 mM GSH eluant were predominantly cGSTM1. A protein (cGSTM1') with an N-terminal amino acid sequence identical to that of cGSTM1 but with the initiator methionine retained and a novel class-mu isozyme (cGSTM2*) were also recovered from this fraction. Nine class-alpha isozymes with distinctive molecular masses were identified from the 1 mM S-hexylglutathione eluant. Three of these proteins are probably variants with minor amino acid substitutions of other isozymes. Of the six remaining class-alpha isozymes, three of them have had their complete (cGSTA1 and cGSTA2) or partial (cGSTA3) cDNA sequences reported previously in the literature. A chicken liver cDNA library was screened with oligonucleotides generated from the cGSTA2 sequence as probes. Clones that encompass the complete coding regions of cGSTA3 and cGSTA4 were obtained. A clone encoding the C-terminal 187 residues of cGSTA5 was also isolated.

Amino acid sequence of glutathione S-transferase rGSTM5* from rat testis

Glutathione S-transferase rGSTM5* was isolated from rat testis with a combination of glutathione affinity column and reverse-phase column chromatography. The protein was digested with Achromobacter protease I or endoproteinase Arg-C. The peptide fragments were isolated for electrospray MS and N-terminal peptide sequencing analyses. The primary amino acid sequence of rGSTM5* comprises 217 residues and has a calculated average molecular mass of 25495.3 Da. The result is identical to that obtained for rGSTM5* with liquid chromatography-MS from a mixture of rat testicular GSTs. Therefore, rGSTM5* has not been post-translationally modified.

Isolation and characterization of a DnaJ-like protein in rats: the C-terminal 10-kDa domain of hsc70 is not essential for stimulating the ATP-hydrolytic activity of hsc70 by a DnaJ-like protein

A DnaJ-like protein, RDJ1, was isolated from a rat brain cDNA library. The protein is predicted to have 397 amino acid residues and shares 99% identity to that of HDJ2, a human DnaJ-like protein. RDJ1 was also shown to rescue the temperature-sensitive lethality of a strain containing a mutated cytosolic DnaJ in yeast, ydj1-151. Fragments containing the J-domain of RDJ1 either with or without the G/F motif were expressed in Escherichia coli. The purified proteins stimulated the ATPase activity of hsc70 and of the 60-kDa N-terminal fragment of hsc70. These results imply that RDJ1 can interact with the N-terminal 60-kDa fragment of hsc70 to activate ATP hydrolysis by hsc70.

Quantitative profiling of tissue- and gender-related expression of glutathione S-transferase isoenzymes in the mouse

Cytosolic glutathione S-transferase (GST) isoenzymes from brain, heart, lung, liver, kidney and gonads of male and female CD-1 mice were identified and quantified with a combination of affinity purification, electrospray ionization MS, Edman microsequencing, Western blot analysis and reverse-phase HPLC. The three principal hepatic GST subunits, mGSTA3 (25271 Da), mGSTP1 (23478 Da), and mGSTM1 (25839 Da), were isolated from liver, lung, kidney, testes and female heart, whereas brain, ovaries and male heart contained mGSTM1 and mGSTP1. Additional isoenzymes were detected in tissues, including mu class subunits mGSTM2 (25580 Da) and mGSTM3 (25570 Da), an N-terminally blocked Alpha subunit (25480 Da) assigned as mGSTA4, and proteins of molecular masses 25490, 22540, 24493, 24378 and 25383 Da. Distinct gender differences in expression of GST subunits were observed for liver, heart, kidney and gonads, whereas GST expression was similar in brain and lung for both genders. In contrast with patterns of expression in liver (high ratio of mGSTA3 to mGSTP1 in females relative to males), mGSTP1 was the most abundant subunit in female gonads, whereas mGSTA3 was not present in detectable quantities. The profile of GST expression in kidney was similar to that in liver; however, male kidneys expressed 30% more soluble GST than female kidneys. A striking gender-related difference in GST expression was found in cardiac tissue, where female animals expressed 50% more soluble GST than male tissues, and the GST isoenzyme with the greatest documented activity towards lipid hydroperoxides, mGSTA3, was present in female tissue yet absent from male tissue. These results point to complex gender- and tissue-dependent expression of individual mouse GST isoenzymes.

Mass spectrometric analysis of rat ovary and testis cytosolic glutathione S-transferases (GSTs): identification of a novel class-alpha GST, rGSTA6*, in rat testis

Cytosolic glutathione S-transferases (GSTs) from rat ovaries and testis were purified by a combination of GSH and S-hexylglutathione affinity chromatography. The isolated GSTs were subjected to reverse-phase HPLC, electrospray MS and N-terminal peptide sequencing analysis. The major GST isoenzymes expressed in ovaries are subunits A3, A4, M1, M2 and P1. Other isoenzymes detected are subunits A1, M3 and M6*. In rat testis, the major GST isoenzymes expressed are subunits A3, M1, M2, M3, M5* and M6*. Subunits A1, A4 and P1 are expressed in lesser amounts. We could not detect post-translational modifications of any GSTs with known cDNA sequence. The molecular masses of subunits M5* and M6*, two class-Mu GSTs that have not been cloned, were determined to be 25495 and 26538 Da respectively. An N-terminally modified protein from rat testis with molecular mass 25737 Da was isolated from the S-hexylglutathione column. Results from internal peptide sequencing analysis indicate that this is a novel class-Alpha GST that has not been previously reported. We designate this protein rGSTA6*.