Homologs of the plastidal preprotein translocase Tic20 mediate organelle assembly in bacteria

Abstract

Organelle-specific protein translocation systems are essential for organelle biogenesis and maintenance in eukaryotes but thought to be absent from prokaryotic organelles. Here, we identified that MamF-like proteins involved in the formation of bacterial magnetosome organelles share an ancient origin with Tic20 protein translocases found in chloroplasts. Deletion of mamF-like genes in the alphaproteobacterium Magnetospirillum gryphiswaldense results in severe defects in organelle positioning, biomineralization, and magnetic navigation. Consistent with translocase-like functions, these defects are caused by the loss of magnetosome targeting of a subset of organellar proteins containing C-terminal glycine-rich integral membrane domains. Our findings suggest that organelle-specific protein translocation systems may indeed play a role in bacterial organelle formation.