, Volume 46, Issue 2, pp 153–161

Biogenesis of mitochondrial porin: The import pathway

  • R. Pfaller
  • R. Kleene
  • W. Neupert
Multi-author Review


We review here the present knowledge about the pathway of import and assembly of porin into mitochondria and compare it to those of other mitochondrial proteins. Porin, like all outer mitochondrial membrane proteins studied so far is made as a precursor without a cleavble ‘signal’ sequence; thus targeting information must reside in the mature sequence. At least part of this information appears to be located at the amino-terminal end of the molecule. Transport into mitochondria can occur post-translationally. In a first step, the porin precursor is specifically recognized on the mitochondrial surface by a protease sensitive receptor. In a second step, porin precursor inserts partially into the outer membrane. This step is mediated by a component of the import machinery common to the import pathways of precursor proteins destined for other mitochondrial subcompartments. Finally, porin is assembled to produce the functional oligomeric form of an integral membrane protein wich is characterized by its extreme protease resistance.

Key words

Porin biogenesis mitochondrial outer membrane import receptors GIP ATP 


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  1. 1.
    Adrian, G. S., McGammon, M. T., Montgomery, D. L., and Douglas, M. G., Sequences required for delivery and localization of ADP/ATP translocator to the mitochondrial inner membrane. Molec. cell. Biol.6 (1986) 626–634.PubMedGoogle Scholar
  2. 2.
    Aquila, H., Link, T., and Klingenberg, M., The uncoupling protein from brown fat mitochondria is related to the mitochondrial ADP/ATP carrier. Analysis of the sequence homologies and of folding of the protein in the membrane. EMBO J.4 (1985) 2369–2376.PubMedGoogle Scholar
  3. 3.
    Aquila, H., Link, T., and Klingenberg, M., Solute carriers involved in energy transfer of mitochondria from a homologous protein family. FEBS Lett.212, (1987) 1–9.PubMedGoogle Scholar
  4. 4.
    Benz, R., Porin from bacterial and mitochondrial outer membranes. CRC Crit. Rev. Biochem.19 (1985) 145–190.PubMedGoogle Scholar
  5. 5.
    Chen, L., and Tai, P. C., ATP is essential for protein translocation inE. coli membrane vesicles. Proc. natl Acad. Sci. USA82 (1985) 4384–4388.PubMedGoogle Scholar
  6. 6.
    Chen, W.-J., and Douglas, M. G., Phosphodiester bond cleavage outside mitochondria is required for the completion of protein import into the mitochondrial matrix. Cell49 (1987) 651–658.PubMedGoogle Scholar
  7. 7.
    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., Mitochondrial heat-shock protein hsp 60 is essential for assembly of proteins imported into yeast mitochondria. Nature337 (1989) 620–625.PubMedGoogle Scholar
  8. 8.
    Chirico, W. J., Waters, M. G., and Blobel, G., 70-kD heat shock related proteins stimulate protein translocation into microsomes. Nature322 (1988) 805–810.Google Scholar
  9. 9.
    Colombini, M., Structure and mode of action of a voltage dependent anion-selective channel (VDAC) located in the outer mitochondrial membrane. Ann. N.Y. Acad. Sci.341 (1980) 552–563.Google Scholar
  10. 10.
    Deshaies, R. J., Koch, B. D., Werner-Washburne, M., Craig, E., and Schekman, R., A subfamily of stress proteins facilitates translocation of secretory and mitochondrial precursor polypeptides. Nature322 (1988) 800–805.Google Scholar
  11. 11.
    Eilers, M., Oppliger, W., and Schatz, G., Both ATP and an energized inner membrane are required to import a purified precursor protein into mitochondria. EMBO J.6 (1987) 1073–1077.PubMedGoogle Scholar
  12. 12.
    Eilers, M., and Schatz, G., Protein unfolding and the energetics of protein translocation across biological membranes. Cell52 (1988) 481–483.PubMedGoogle Scholar
  13. 13.
    Flügge, U. I., and Hinz, G., Energy dependence of protein translocation into chloroplasts. Eur. J. Biochem.160 (1986) 563–570.PubMedGoogle Scholar
  14. 14.
    Freitag, H., Genchi, G., Benz, R., Palmieri, F., and Neupert, W., Isolation of mitochondrial porin fromNeurospora crassa. FEBS Lett.145 (1982) 72–76.PubMedGoogle Scholar
  15. 15.
    Freitag, H., Janes, M., and Neupert, W., Biosynthesis of mitochondrial porin and insertion into the outer mitochondrial membrane ofNeurospora crassa. Eur. J. Biochem.126 (1982) 197–202.PubMedGoogle Scholar
  16. 16.
    Freitag, H., Neupert, W., and Benz, R., Purification and characterisation of a pore protein of the outer mitochondrial membrane fromNeurospora crassa. Eur. J. Biochem.123 (1982) 629–636.PubMedGoogle Scholar
  17. 17.
    Gasser, S. M., Daum, G., and Schatz, G., Import of proteins into mitochondria. Energy-dependent uptake of precursors by isolated mitochondria. J. biol. Chem.257 (1982) 13034–13041.PubMedGoogle Scholar
  18. 18.
    Gasser, S. M., and Schatz, G., Import of proteins into mitochondria: In vitro studies on the biogenesis of the outer membrane. J. biol. Chem.258 (1983) 3427–3430.PubMedGoogle Scholar
  19. 19.
    Geller, B. L., Movva, N. R., and Wickner, W., Both ATP and the electrochemical potential are required for optimal assembly of pro-Omp A intoEscherichia coli inner membrane vesicles. Proc. natl Acad. Sci. USA83 (1986) 4219–4222.PubMedGoogle Scholar
  20. 20.
    Grossmann, A., Bartlett, S., and Chua, N. H., Energy-dependent uptake of cytoplasmically synthesized polypeptides by chloroplasts. Nature285 (1980) 625–628.Google Scholar
  21. 21.
    Hallermayer, G., and Neupert, W., Lipid composition of mitochondrial outer and inner membranes ofNeurospora crassa. Hoppe Seyler's Z. physiol. Chem.355 (1974) 279–288.PubMedGoogle Scholar
  22. 22.
    Hamajima, S., Sakaguchi, M., Mihara, K., Ono, S., and Sato, R., Both amino- and carboxy-terminal portions are required for insertion of yeast porin into the outer mitochondrial membrane. J. Biochem.104 (1988) 362–367.PubMedGoogle Scholar
  23. 23.
    Hansen, W., Garcia, P. D., and Walter, P., In vitro protein translocation in yeast endoplasmatic reticulum: ATP-dependent post-translational translocation of the prepro-a factor. Cell45 (1986) 397–406.PubMedGoogle Scholar
  24. 24.
    Hartl, F.-U., Pfanner, N., Nicholson, D. W., and Neupert, W., Mitochondrial protein import. Biochim. biophys. Acta988 (1989) 1–45.Google Scholar
  25. 25.
    Hase, T., Müller, U., Riezman, H., and Schatz, G., A 70-kD protein of the yeast mitochondrial outer membrane is targeted and anchored via its extreme amino terminus. EMBO J.3 (1984) 3157–3164.PubMedGoogle Scholar
  26. 26.
    Hawlitschek, G., Schneider, H., Schmidt, B., Tropschug, M., Hartl, F.-U., and Neupert, W., Mitochondrial protein import: Identification of processing peptidase and of PEP, a processing enhancing protein. Cell53 (1988) 795–806.PubMedGoogle Scholar
  27. 27.
    Horwich, A. L., Kalousek, F., Mellman, I., and Rosenberg, L. E., A leader peptide is sufficient to direct mitochondrial import of a chimeric protein. EMBO J.4 (1985) 1129–1135.PubMedGoogle Scholar
  28. 28.
    Hurt, E. C., Müller, U., and Schatz, G., The first twelve amino acids of a yeast mitochondrial outer membrane protein can direct a nuclearencoded cytochrome oxidase subunit to the mitochondrial inner membrane. EMBO J.4 (1985) 3509–3518.PubMedGoogle Scholar
  29. 29.
    Hurt, E. C., Pesold-Hurt, B., and Schatz, G., The cleavable prepiece of an imported mitochondrial protein is sufficient to direct cytosolic dihydrofolate reductase into the mitochondrial matrix. FEBS Lett.178 (1984) 306–310.PubMedGoogle Scholar
  30. 30.
    Hurt, E. C., Pesold-Hurt, B., and Schatz, G., The amino terminal region of an imported mitochondrial precursor polypeptide can direct cytoplasmic dihydrofolate reductase into mitochondrial matrix. EMBO J.3 (1984) 3149–3156.PubMedGoogle Scholar
  31. 31.
    Hurt, E. C., and van Loon, A. P. G. M., How proteins find mitochondria and intramitochondrial compartments. Trends biochem. Sci.11 (1986) 204–207.Google Scholar
  32. 32.
    Imanaka, T., Small, G. M., and Lazarow, P. B., Translocation of Acyl-CoA oxidase into peroxisomes requires ATP hydrolysis but not a membrane potential. J. Cell Biol.105 (1987) 2915–2922.PubMedGoogle Scholar
  33. 33.
    Jaenicke, R., and Rudolph, R., Refolding and association of oligomeric proteins. Methods Enzym.131 (1986) 218–250.Google Scholar
  34. 34.
    Jensen, R. E., and Yaffe, M. P., Import of proteins into yeast mitochondria: the nuclear MAS2 gene encodes a component of the processing protease that is homologous to the MAS1-encoded subunit. EMBO J.7 (1988) 3863–3871.PubMedGoogle Scholar
  35. 35.
    Kleene, R., Pfanner, N., Pfaller, R., Link, T.A., Sebald, W., Neupert, W., and Tropschug, M., Mitochondrial porin ofNeurospora crassa: cDNA cloning, in vitro expression and import into mitochondria. EMBO J.6 (1987) 2627–2633.PubMedGoogle Scholar
  36. 36.
    Kolansky, D. M., Conboy, J. G., Fenton, W. A., and Rosenberg, L. E., Energy-dependent translocation of the precursor of ornithine transcarbamylase by isolated rat liver mitochondria. J. biol. Chem.257 (1982) 8467–8471.PubMedGoogle Scholar
  37. 37.
    Linden, M., and Gellerfors, P., Hydrodynamic properties of porin isolated from outer membranes of rat liver mitochondria. Biochim. biophys. Acta736 (1983) 125–129.PubMedGoogle Scholar
  38. 38.
    Mihara, K., Blobel, G., and Sato, R., In vitro synthesis and integration into mitochondria of porin, a major protein of the outer mitochondrial membrane ofSaccharomyces cerevisiae. Proc. natl Acad. Sci. USA79 (1982) 7102–7106.PubMedGoogle Scholar
  39. 39.
    Mihara, K., and Sato, R., Molecular cloning and sequencing of cDNA for yeast porin, an outer mitochondrial membrane protein: a search for targeting signal in the primary structure. EMBO J.4 (1985) 769–774.PubMedGoogle Scholar
  40. 40.
    Mueckler, M., and Lodish, H. F., Post-translational insertion of a fragment of the glucose transporter into microsomes requires phosphoanhydride bond cleavage. Nature322 (1986) 549–552.PubMedGoogle Scholar
  41. 41.
    Murakami, H., Pain, D., and Blobel, G., 70-kD Heat shock-related protein is one of at least two distinct cytosolic factors stimulating protein import into mitochondria. J. Cell Biol.107 (1989) 2052–2057.Google Scholar
  42. 42.
    Nicholson, D. W., Hergersberg, C., and Neupert, W., Role of cytochromec heme lyase in the import of cytochromec into mitochondria. J. biol. Chem.263 (1988) 19034–19042.PubMedGoogle Scholar
  43. 43.
    Ono, H., and Tuboi, S., Integration of porin synthesized in Vitro into outer mitochondrial membranes. Eur. J. Biochem.169 (1987) 509–514.Google Scholar
  44. 44.
    Pfaller, R., Freitag, H., Harmey, M. A., Benz, R., and Neupert, W., A water-soluble form of porin from the mitochondrial outer membrane ofNeurospora crassa: Properties and relationship to the biosynthetic precursor form. J. biol. Chem.260 (1985) 8188–8193.PubMedGoogle Scholar
  45. 45.
    Pfaller, R., and Neupert, W., High-affinity binding sites involved in the import of porin into mitochondria, EMBO J.6 (1987) 2635–2642.PubMedGoogle Scholar
  46. 46.
    Pfaller, R., Steger, F. H., Rassow, J., Pfanner, N., and Neupert, W., Import pathways of precursor proteins into mitochondria: multiple receptor sites are followed by a common membrane insertion site. J. Cell Biol.107 (1988) 2483–2490.PubMedGoogle Scholar
  47. 47.
    Pfanner, N., Hartl, F.-U., and Neupert, W., Import of proteins into mitochondria: a multi-step process. Eur. J. Biochem.175 (1988) 205–212.PubMedGoogle Scholar
  48. 48.
    Pfanner, N., Hoeben, P., Tropschug, M., and Neupert, W., The carboxyl-terminal two-thirds of the ATP/ATP carrier polypeptide contains sufficient information to direct translocation into mitochondria. J. biol. Chem.262 (1987) 14851–14854.PubMedGoogle Scholar
  49. 49.
    Pfanner, N., and Neupert, W., Transport of proteins into mitochondria: a potassium diffusion potential is able to drive the import of ADP/ATP carrier. EMBO J.4 (1985) 2819–2825.PubMedGoogle Scholar
  50. 50.
    Pfanner, N., and Neupert, W., Transport of F1-ATPase subunit β into mitochondria depends on both a membrane potential and nucleoside triphosphates. FEBS Lett.209 (1986) 152–156.PubMedGoogle Scholar
  51. 51.
    Pfanner, N., and Neupert, W., Distinct steps in the import of ADP/ATP carrier into mitochondria. J. biol. Chem.262 (1987) 7528–7536.PubMedGoogle Scholar
  52. 52.
    Pflanner, N., Pfaller, R., Kleene, R., Ito, M., Tropschug, M., and Neupert, W., Role of ATP in mitochondrial protein import: Conformational alteration of a precursor protein can substitute for ATP requirement. J. biol. Chem.263 (1988) 4049–4051.PubMedGoogle Scholar
  53. 53.
    Pfanner, N., Tropschug, M., and Neupert, W., Mitochondrial protein import: Nucleoside triphosphates are involved in conferring import-competence to precursors. Cell49 (1987) 815–823.PubMedGoogle Scholar
  54. 54.
    Pollock, R. A., Hartl, F.-U., Cheng, M. Y., Ostermann, J., Horwich, A., and Neupert, W., The processing peptidase of yeast mitochondria: the two co-operating components MPP and PEP are structurally related. EMBO J.7 (1988) 3493–3500.PubMedGoogle Scholar
  55. 55.
    Roise, D., Horvath, S. J., Tomich, J. M., Richards, J. H., and Schatz, G., A chemically synthesized pre-sequence of an imported mitochondrial protein can form an amphiphilic helix and perturb natural and artificial phospholipid bilayers. EMBO J.5 (1986) 1327–1334.PubMedGoogle Scholar
  56. 56.
    Rothblatt, J. A., and Meyer, D. I., Secretion in yeast: Translocation and glycosylation of prepro-a-factor in vitro can occur via an ATP-dependent post-translational mechanism. EMBO J.5 (1986) 1031–1036.PubMedGoogle Scholar
  57. 57.
    Schleyer, M., Schmidt, B., and Neupert, W., Requirement of a membrane potential for the posttranslational transfer of proteins into mitochondria. Eur. J. Biochem.125 (1982) 109–116.PubMedGoogle Scholar
  58. 58.
    Schleyer, M., and Neupert, W., Transport of proteins into mitochondria: Translocational intermediates spanning contact sites between outer and inner membranes. Cell43 (1985) 339–350.PubMedGoogle Scholar
  59. 59.
    Schmidt, B., Pfaller, R., Pfanner, N., Schleyer, M., and Neupert, W., Transport of proteins into mitochondria: receptors, recognition and transmembrane movement of precursors in: Achievements and Perspectives of Mitochondrial Research, vol. II, pp. 389–396. Eds E. Quagliariello, E. C. Slater, F. Palimieri, C. Saccone and A. M. Kroon. Elsevier Science Publishers, Amsterdam 1985.Google Scholar
  60. 60.
    Schwaiger, M., Herzog, V., and Neupert, W., Characterization of translocation contact sites involved in the import of mitochondrial proteins. J. Cell Biol.105 (1987) 235–246.PubMedGoogle Scholar
  61. 61.
    Smagula, C., and Douglas, M. G., Mitochondrial import of the ADP-ATP carrier protein inSaccharomyces cerevisiae: Sequences required for receptor binding and membrane translocation. J. biol. Chem.263 (1988) 6783–6790.PubMedGoogle Scholar
  62. 62.
    Stuart, R. A., Neupert, W., and Tropschug, M., Deficiency in mRNA splicing in a cytochromec mutant ofNeurospora crassa: importance of carboxy terminus for import of apocytochromec into mitochondria. EMBO J.6 (1987) 2131–2137.PubMedGoogle Scholar
  63. 63.
    Vestweber, D., and Schatz, G., A chimeric mitochondrial precursor protein with internal disulfide bridges blocks import of authentic precursors into mitochondria and allows quantitation of import sites. J. Cell Biol.107 (1988) 2037–2043.PubMedGoogle Scholar
  64. 64.
    von Heijne, G., Mitochondrial targeting sequences may form amphiphilic helices. EMBO J.5 (1986) 1335–1342.PubMedGoogle Scholar
  65. 65.
    Waters, M. G., and Blobel, G. Secretory protein translocation in a yeast cell-free system can occur post-translationally and requires ATP hydrolysis. J. Cell Biol.102 (1986) 1543–1550.PubMedGoogle Scholar
  66. 66.
    Witte, C., Jensen, R. E., Yaffe, M. P., and Schatz, G., MAS1, a gene essential for yeast mitochondrial assembly, encodes a subunit of the mitochondrial processing protease. EMBO J.7 (1988) 1439–1447.PubMedGoogle Scholar
  67. 67.
    Wiech, H., Sagstetter, M., Müller, G., and Zimmermann R., The ATP requiring step in assembly of M13 procoat protein into microsomes is related to preservation of transport competence of the precursor protein. EMBO J.6 (1987) 1011–1016.PubMedGoogle Scholar
  68. 68.
    Yaffe, M. P., Ohta, S., and Schatz, G., A yeast mutant temperaturesensitive for mitochondrial assembly is deficient in a mitochondrial protease activity that cleaves imported precursor polypeptides. EMBO J.4 (1985) 2069–2074.PubMedGoogle Scholar
  69. 69.
    Yang, M., Jensen, R. E., Yaffe, M. P., Oppliger W., and Schatz, G., Import of proteins into yeast mitochondria: the purified matrix processing peptidase contains two subunits which are encoded by the nuclear MAS1 and MAS2 genes. EMBO J.7 (1988) 3857–3862.PubMedGoogle Scholar
  70. 70.
    Zimmermann, R., Hennig, B., and Neupert, W., Different transport pathways of individual precursor proteins into mitochondria. Eur. J. Biochem.116 (1981) 455–560.PubMedGoogle Scholar
  71. 71.
    Zwizinski, C., Schleyer, M., and Neupert, W., Transfer of proteins into mitochondria: Precursor to the ADP/ATP carrier binds to receptors sites on isolated mitochondria. J. biol. Chem.258 (1983) 4071–4074.PubMedGoogle Scholar
  72. 72.
    Zwizinski, C., Schleyer, M., and Neupert, W., Proteinaceous receptors for the import of mitochondrial precursor proteins. J. biol. Chem.259 (1984) 7850–7856.PubMedGoogle Scholar

Copyright information

© Birkhäuser Verlag 1990

Authors and Affiliations

  • R. Pfaller
    • 1
  • R. Kleene
    • 1
  • W. Neupert
    • 1
  1. 1.Institut für Physiologische Chemie der Universität MünchenMünchen 2(Federal Republic of Germany)

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