CHARACTERIZATION OF A GLUTATHIONE-S-TRANSFERASE AND A RELATED GLUTATHIONE-BINDING PROTEIN FROM GILL OF THE BLUE MUSSEL, MYTILUS-EDULIS

The major isoenzyme of glutathione S-transferase (GST 1) was purified to homogeneity from cytosolic extracts of Mytilus edulis gill tissue b y GSH-agarose affinity chromatography followed by Mono Q ion-exchange f.p.l.c. This enzyme was particularly active with 1-chloro-2,4-dinitro benzene, ethacrynic acid and cumene hydroperoxide as substrates. Immun oblotting and amino acid sequencing studies indicate that the enzyme b elongs to the Pi class of GSTs. A related protein which binds to GSH-a garose was also purified. This GSH-binding protein did not immunoblot with GST antisera and showed no detectable catalytic activity with GST substrates although its N-terminal sequence was similar to Mu-class G STs. Gel-filtration chromatography indicated that GST 1 is a dimer and the GSH-binding protein a monomer. Mass spectrometry and SDS/PAGE ind icate subunit molecular masses of 24 kDa (GST 1) and 25 kDa (GSH-bindi ng protein), respectively. Both proteins have amino acid compositions typical of GSTs.