The alpha regulatory subunit of the mitochondrial F1-ATPase complex is a heat-shock protein. Identification of two highly conserved amino acid sequences among the alpha-subunits and molecular chaperones

Abstract

The recent identification of the alpha-subunit of mitochondrial F1-ATPase complex in rat liver peroxisomes suggests another functional role for this protein in both organelles in addition to its involvement in mitochondrial oxidative phosphorylation. We report here that a very rapid response (15 min) in the induction of the alpha-regulatory subunit of the mitochondrial F1-ATPase complex is observed in 37 degrees C heat-shocked larvae of Drosophila hydei. Under the same heat-shock treatment, a similar-fold induction for the heat-shock protein hsp-70 was less rapid (45 min). Although the amino acid sequence identities between the "chaperonine" and the alpha-subunit protein families are very low (less than 20%), two amino acid sequences, of 12 and 13 residues each, are found in the alpha-subunits of the F1-ATPase complex from various eukaryotes which show a highly conserved identity (over 50%) with amino acid sequences found in molecular chaperones. We suggest that the nuclear coded alpha-subunit belongs to the family of stress proteins hsp-60 and thus, that it could perform similar functional role(s) to those recently described for mitochondrial hsp-60 (Cheng, M. Y., Hartl, F. U., Martin, J., Pollock, R. A., Kalousek, F., Neupert, W., Hallberg, E. M., Hallberg, R. L., and Horwich, A. L. (1989) Nature 337, 620-625 and Ostermann, J., Horwich, A. L., Neupert, W., and Ultrich-Hartl, F. (1989) Nature 341, 125-130) in both the mitochondria and the peroxisomes. Furthermore, we suggest that the two conserved elements among the chaperonines and the alpha-subunits could putatively be involved in the chaperonine function of these proteins.