Experimental determination of membrane orientation of six T. brucei FtsH subunits.
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Two groups of FtsH subunits were present in the last eukaryotic common ancestor.
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FtsH subunits of kinetoplastids have undergone a unique evolution.
Abstract
Trypanosoma brucei is an important human pathogen. In this study, we have focused on the characterization of FtsH protease, ATP-dependent membrane-bound mitochondrial enzyme important for regulation of protein abundance. We have determined localization and orientation of all six putative T.brucei FtsH homologs in the inner mitochondrial membrane by in silico analyses, by immunofluorescence, and with protease assay. The evolutionary origin of these homologs has been tested by comparative phylogenetic analysis. Surprisingly, some kinetoplastid FtsH proteins display inverted orientation in the mitochondrial membrane compared to related proteins of other examined eukaryotes. Moreover, our data strongly suggest that during evolution the orientation of FtsH protease in T. brucei varied due to both loss and acquisition of the transmembrane domain.
Abbreviations
AAA
ATPases associated with various functions
DIG
concentration of digitonin in mg per mg of cell proteins (w/w)