PROTEIN DEPLETION AND REFEEDING CHANGE THE PROPORTION OF MOUSE-LIVER GLUTATHIONE-S-TRANSFERASE SUBUNITS

The effect of protein depletion followed by refeeding with a normal di et on the content of mouse liver cytosolic proteins was studied, By pe ptide-mass fingerprinting and N-terminal sequencing, three polypeptide s whose contents changed with dietary protein level were identified as glutathione S-transferases (GST) Yb1, Ye and Yf subunits. Five days o f depletion caused the increase of Yb1 and Yf (21.6% and 78.5%, respec tively) and the decrease of Ye (31.2%). After two days of refeeding, Y b1 and Ye were practically restored, while the neoplastic marker Yf re mained higher (63.4%), None of the nutritional conditions tested induc ed new GSTs. While protein depletion-refeeding altered the ratios betw een the constitutive GST subunits, total liver GST content and activit y were unaffected by depletion and slightly increased by refeeding. Th e increased amounts of Yb1 and Yf, and the maintenance of total GST co ntent, indicate that during protein depletion, the GST subunits levels are controlled by mechanisms different from the majority of cytosolic proteins. (C) 1997 Elsevier Science B.V.