Mitochondrial Porin VDAC 1 Seems to Be Functional in Rickettsial Cells

Author: Emelyanov, Victor V.

Source: Annals of the New York Academy of Sciences, Volume 1166, Number 1, May 2009 , pp. 38-48(11)

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Abstract:

We have recently shown that Rickettsia prowazekii (typhus group rickettsiae) cells incorporate human mitochondrial porin VDAC1. Here, I report on the import of porin by rickettsiae of spotted fever group. It was shown that rickettsial cells of heavy band of Renografin density gradient, known as permeabilized rickettsiae, contain much more VDAC 1 compared to the cells of light band, that is, non-permeabilized rickettsiae. These data hint at a functionality of mitochondrial porin in rickettsial cells. The cells of Rickettsia canadensis were broken in French-press, and total membranes were fractionated on linear sucrose density gradient. In this way, previous data were confirmed that an outer rickettsial membrane does not contain porin, while fraction of intermediate density, which likely represents Bayer's adhesion zones, is enriched in VDAC 1. This is consistent with earlier results and their interpretation that imported porin seems to localize to contact sites between inner and outer rickettsial membranes. Based on well-known phylogenetic relationship of Rickettsiales and mitochondria, an evolutionary scenario for the origin of protein import machinery is proposed. A dependence of rickettsiae upon essential protein(s), destined to organelle, is also viewed as a nature of their obligate endosymbiotic lifestyle.

Keywords: rickettsiae; mitochondria; common evolutionary origin; protein import; beta-barrel proteins; mitochondrial porin; obligate endosymbiosis

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1749-6632.2009.04513.x

Affiliations: 1: Institute of Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom

Publication date: 2009-05-01