The mitochondrial protein import motor

被引:39
作者
Strub, A
Lim, JH
Pfanner, N
Voos, W
机构
[1] Univ Freiburg, Inst Biochem & Mol Biol, D-79104 Freiburg, Germany
[2] Univ Freiburg, Fak Biol, D-79104 Freiburg, Germany
关键词
heat shock protein; Mge1; mitochondria; mtHsp70; protein import; Tim44;
D O I
10.1515/BC.2000.115
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Mitochondrial proteins are synthesized as precursor proteins in the cytosol and are posttranslationally imported into the organelle. A complex system of translocation machineries recognizes and transports the precursor polypeptide across the mitochondrial membranes. Energy for the translocation process is mainly supplied by the mitochondrial membrane potential (Delta psi) and the hydrolysis of ATP. Mitochondrial Hsp70 (mtHsp70) has been identified as the major ATPase driving the membrane transport of the precursor polypeptides into the mitochondrial matrix. Together with the partner proteins Tim44 and Mge1, mtHsp70 forms an import motor complex interacting with the incoming preproteins at the inner face of the inner membrane. This import motor complex drives the movement of the polypeptides in the translocation channel and the unfolding of carboxy-terminal parts of the preproteins on the outside of the outer membrane. Two models of the molecular mechanism of mtHsp70 during polypeptide translocation are discussed. In the 'trapping' model, precursor movement is generated by Brownian movement of the polypeptide chain in the translocation pore. This random movement is made vectorial by the interaction with mtHsp70 in the matrix. The detailed characterization of conditional mutants of the import motor complex provides the basis for an extended model. In this 'pulling' model, the attachment of mtHsp70 at the inner membrane via Tim44 and a conformational change induced by ATP results in the generation of an inward-directed force on the bound precursor polypeptide. This active role of the import motor complex is necessary for the translocation of proteins containing tightly folded domains. We suggest that both mechanisms complement each other to reach a high efficiency of preprotein import.
引用
收藏
页码:943 / 949
页数:7
相关论文
共 33 条
  • [1] Multiple interactions of components mediating preprotein translocation across the inner mitochondrial membrane
    Bomer, U
    Meijer, M
    Maarse, AC
    Honlinger, A
    Dekker, PJT
    Pfanner, N
    Rassow, J
    [J]. EMBO JOURNAL, 1997, 16 (09) : 2205 - 2216
  • [2] Separation of structural and dynamic functions of the mitochondrial translocase:: Tim44 is crucial for the inner membrane import sites in translocation of tightly folded domains, but not of loosely folded preproteins
    Bömer, U
    Maarse, AC
    Martin, F
    Geissler, A
    Merlin, A
    Schönfisch, B
    Meijer, M
    Pfanner, N
    Rassow, J
    [J]. EMBO JOURNAL, 1998, 17 (15) : 4226 - 4237
  • [3] The Hsp70 and Hsp60 chaperone machines
    Bukau, B
    Horwich, AL
    [J]. CELL, 1998, 92 (03) : 351 - 366
  • [4] Strong precursor-pore interactions constrain models for mitochondrial protein import
    Chauwin, JF
    Oster, G
    Glick, BS
    [J]. BIOPHYSICAL JOURNAL, 1998, 74 (04) : 1732 - 1743
  • [5] Role of mitochondrial GrpE and phosphate in the ATPase cycle of matrix Hsp70
    Dekker, PJT
    Pfanner, N
    [J]. JOURNAL OF MOLECULAR BIOLOGY, 1997, 270 (03) : 321 - 327
  • [6] The Tim core complex defines the number of mitochondrial translocation contact sites and can hold arrested preproteins in the absence of matrix Hsp70-Tim44
    Dekker, PJT
    Martin, F
    Maarse, AC
    Bomer, U
    Muller, H
    Guiard, B
    Meijer, M
    Rassow, J
    Pfanner, N
    [J]. EMBO JOURNAL, 1997, 16 (17) : 5408 - 5419
  • [7] A DUAL ROLE FOR MITOCHONDRIAL HEAT-SHOCK PROTEIN-70 IN MEMBRANE TRANSLOCATION OF PREPROTEINS
    GAMBILL, BD
    VOOS, W
    KANG, PJ
    MIAO, BJ
    LANGER, T
    CRAIG, EA
    PFANNER, N
    [J]. JOURNAL OF CELL BIOLOGY, 1993, 123 (01) : 109 - 117
  • [8] Unfolding of preproteins upon import into mitochondria
    Gaume, B
    Klaus, C
    Ungermann, C
    Guiard, B
    Neupert, W
    Brunner, M
    [J]. EMBO JOURNAL, 1998, 17 (22) : 6497 - 6507
  • [9] CAN HSP70 PROTEINS ACT AS FORCE-GENERATING MOTORS
    GLICK, BS
    [J]. CELL, 1995, 80 (01) : 11 - 14
  • [10] Molecular chaperones in cellular protein folding
    Hartl, FU
    [J]. NATURE, 1996, 381 (6583) : 571 - 580