Journal article

Alternative function for the mitochondrial SAM complex in biogenesis of α-helical TOM proteins

Diana Stojanovski, Bernard Guiard, Vera Kozjak-Pavlovic, Nikolaus Pfanner, Chris Meisinger

Journal of Cell Biology | Rockefeller University Press | Published : 2007

Abstract

The mitochondrial outer membrane contains two preprotein translocases: the general translocase of outer membrane (TOM) and the β-barrel–specific sorting and assembly machinery (SAM). TOM functions as the central entry gate for nuclear-encoded proteins. The channel-forming Tom40 is a β-barrel protein, whereas all Tom receptors and small Tom proteins are membrane anchored by a transmembrane α-helical segment in their N- or C-terminal portion. Synthesis of Tom precursors takes place in the cytosol, and their import occurs via preexisting TOM complexes. The precursor of Tom40 is then transferred to SAM for membrane insertion and assembly. Unexpectedly, we find that the biogenesis of α-helical To..

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