Cytosolic Reactions in Mitochondrial Protein Import

  • Douglas M. Cyr
  • Michael G. Douglas
Conference paper
Part of the NATO ASI Series book series (volume 74)


Cytosolic hsp70 molecules are involved in maintenance of pre-proteins in transport competent conformations. Genetic and biochemical studies in procaryotes indicate that hsp70 (DnaK) functionally interacts with two other cytosolic proteins, DnaJ and GrpE (Ang et al., 1991). Recently, several eukaryotic DnaJ homologs have been identified. We have purified cytosolic hsp70 (SSA1p) and DnaJ (YDJ1p) homologs from S. cerevisiae and characterized interactions between them. SSA1p exhibited a weak ATPase activity which was stimulated about 10 fold by YDJ1p. Stable complex formation between SSA1p and a mitochondria) presequence peptide was demonstrated. Significant reductions in complex formation were only observed in the presence of both ATP and YDJ1 p. Thus, an eukaryotic dnaJ homolog functionally interacts an eukaryotic hsp70 family member to regulate affinity of the chaperone for a polypeptide substrate.


Heat Shock Transcription Factor Nascent Polypeptide Chain Hsp70 Homolog Cell BioI Mitochondrial Protein Import 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ang, D, Liberek, K, Skowyra, D, Zylicz, M and Georgopoulos, C (1991). Biological role and regulation of the universally conserved heat shock proteins. J Biol. Chem 266: 24233–24236.PubMedGoogle Scholar
  2. Atencio, D P and Yaffe, M P (1992). MASS, a yeast homolog of dnaJ involved in mitochondrial protein import. Mol Cell Biol 12: 283–291.PubMedGoogle Scholar
  3. Bork, P, Sander, C and Valencia, A (1992). A module of the dnaJ heat sock proteins found in malaria parasites. TIBS 17: 29. 2.Google Scholar
  4. Beckman, R P, Mizzen, L A and Welch, W J (1990) Interaction of hsp70 with newly synthesized proteins: Implications for protein folding and assembly. Science 248: 850–854.CrossRefGoogle Scholar
  5. Caplan, A J and Douglas, M G (1991). Characterization of YDJ1: A yeast homologue of the E.coli dnaJ gene. J Cell Biol 114: 609–622.PubMedCrossRefGoogle Scholar
  6. Caplan, A J, Tsai, J, Casey, P J and Douglas, M G (1992). Farnesylation of YDJ1p is required for function at elevated temperatures in S.cerevisiae. J Biol Chem In press. Cyr, D M, Lu, X L and Douglas M G (1992) Regulation of eukaryotic hsp70 by a dna homolog (submitted).Google Scholar
  7. Cyr, D M and Douglas M G (1991) Early events in the transport of proteins into mitochondria: Import competition by a mitochondrial presequence J Biol Chem 266: 21700–21708.Google Scholar
  8. Chirico, W J, Waters, M G and Blobel. 1988. 70K heat shock related proteins stimulate protein translocation into microsomes. Nature 332: 805–810.PubMedCrossRefGoogle Scholar
  9. Deshaies, R J, B D Koch, M Werner-Washburne, E A Craig, and R Schekman. (1988). A subfamily of stress proteins facilitates translocation of secretory and mitochondrial precursor polypeptides. Nature 332: 800–805.PubMedCrossRefGoogle Scholar
  10. Gamer, J, Bujard, H and Bukau, B (1992). Physical interactions between heat shock proteins dnaK, dnaJ and grpE and the bacterial heat shock transcription factor a32. Cell 69: 833–842.PubMedCrossRefGoogle Scholar
  11. Gething, M-J, and Sambrook, J (1992). Protein folding in the cell. Nature 355: 33–45.PubMedCrossRefGoogle Scholar
  12. Langer, T, Lu, C, Echols, H,Flanagan, J, Hayer, M.K and Hartl, F-U (1992). Successive action of dnaK, dnaJ and GroEL along the pathway of chaperone-mediated protein folding. Nature 356: 6883–6889.CrossRefGoogle Scholar
  13. Liberek, K, Marszalek,J, Ang, D, Georgopoulos, C and Zylicz, M (1991a) Escherichia coli dnaJ and grpE heat shock proteins jointly stimulate ATPase acitivity of dnaK. Proc Nat Acad Sci (U.S.A.). 88: 2874–2878.CrossRefGoogle Scholar
  14. Liberek,K, Skowyra,D, Zylic, M, Johnson, C. and Georgopoulos (1991b) The E. coli DnaK chaperone, the 70-Kda heat shoch protein eukaryotic equivalent, changes conformation upon ATP hydrolysis, thus triggering its dissociation from bound traget protein. J Biol Chem. 266: 14491–96.PubMedGoogle Scholar
  15. Widmer, S, Hoskins, J and McKenny, K (1991) Function of dnaJ and dnaK as chaperones in origin-specific DNA binding by RepA. Nature 350: 165–167CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1993

Authors and Affiliations

  • Douglas M. Cyr
    • 1
  • Michael G. Douglas
    • 1
  1. 1.Department of Biochemistry and BiophysicsUniversity of North CarolinaChapel HillUSA

Personalised recommendations