Mitochondrial TatB plays a critical role in the biogenesis of complex III in plant mitochondria Kerstin Schäfer1, Jürgen Soll2 and Chris Carrie1 1Department of Biology I, Botany, Ludwig-Maximilians-Universität München, Großhaderner Strasse 2-4, Planegg-Martinsried D-82152, Germany; 2Department of Biology I, Botany, Ludwig-Maximilians-Universität München, Großhaderner Strasse 2-4, Planegg-Martinsried D-82152, Germany Munich Center for Integrated Protein Science, CiPSM, Ludwig-Maximilians-University Munich, Feodor-Lynen-Strasse 25, Munich D-81377, Germany
In contrast to the mitochondria from humans and yeast, it has been proposed that plant mitochondria contain a twin arginine translocation (Tat) pathway. Tat pathways have been extensively studied in bacteria and chloroplasts and are responsible for the translocation of fully folded proteins across and into the bacterial cytoplasmic membrane or thylakoid membranes of chloroplasts. It was previously demonstrated that plant mitochondria contain two proteins related to Tat components from bacteria and chloroplasts however, no function has ever been attributed to them. It was proposed that because plant mitochondria also lack the Bcs1 protein, a potential target of the plant mitochondrial Tat pathway was the Rieske Fe-S protein from complex III. This was supported by knowledge that the Tat pathways of bacteria and chloroplasts also transport Rieske Fe-S proteins. Here, we demonstrate that C-terminal deletion mutants of the plant mitochondrial TatB (mTatB) protein lead to a severe growth and male sterile phenotype in Arabidopsis thaliana. Further investigations have led to the conclusion that a defect in complex III biogenesis is the underlying reason for the severe phenotypes observed. The defect in complex III biogenesis was traced back to failure to properly insert the Rieske Fe-S protein into complex III.
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