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Mitochondrial porin VDAC 1 seems to be functional in rickettsial cells

Victor V Emelyanov1

  • 1Institute of Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom. Victor.Emelyanov@ncl.ac.uk

Annals of the New York Academy of Sciences
|June 23, 2009
PubMed

Insights

Spotted fever group rickettsiae import mitochondrial porin VDAC1, suggesting a functional role within the bacteria. This import may be linked to their obligate endosymbiotic lifestyle.

Area of Science:

  • Microbiology
  • Cell Biology
  • Evolutionary Biology

Background:

  • Rickettsia prowazekii, a typhus group rickettsia, has been shown to incorporate human mitochondrial porin VDAC1.
  • Porins are crucial protein channels in mitochondrial outer membranes.

Purpose of the Study:

  • To investigate the import of porin by spotted fever group rickettsiae.
  • To explore the localization and potential function of imported porin within rickettsial cells.
  • To propose an evolutionary scenario for the origin of protein import machinery in Rickettsiales.

Main Methods:

  • Differential ultracentrifugation of Rickettsia canadensis cells in Renografin density gradients.
  • Fractionation of total membranes via linear sucrose density gradients after French-press lysis.
  • Analysis of VDAC1 content in different rickettsial membrane fractions.

Main Results:

  • Rickettsial cells from the heavy band (permeabilized) contained significantly more VDAC1 than cells from the light band (non-permeabilized).
  • Outer rickettsial membranes lacked porin, while an intermediate density fraction, likely representing Bayer's adhesion zones, was enriched in VDAC1.
  • Imported porin appears to localize to contact sites between the inner and outer rickettsial membranes.

Conclusions:

  • Mitochondrial porin VDAC1 is imported by spotted fever group rickettsiae, hinting at a functional role.
  • The localization of VDAC1 to contact sites suggests involvement in inter-membrane interactions.
  • The findings support an evolutionary link between Rickettsiales and mitochondria, potentially explaining their obligate endosymbiotic nature.

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