J Integr Plant Biol. ›› 2022, Vol. 64 ›› Issue (8): 1596-1613.DOI: 10.1111/jipb.13312

• Molecular Physiology • Previous Articles     Next Articles

Both metaxin and Tom20 together with two mitochondria-specific motifs support mitochondrial targeting of dual-targeting AtSufE1

Seungjin Woo, Byeongho Moon and Inhwan Hwang*   

  1. Department of Life Sciences, Pohang University of Science and Technology, Pohang 790- 784, Korea

    *Correspondence: Inhwan Hwang (ihhwang@postech.ac.kr)
  • Received:2022-03-14 Accepted:2022-06-14 Online:2022-06-17 Published:2022-08-01


Plant cells have two endosymbiotic organelles, chloroplasts, and mitochondria. These organelles perform specific functions that depend on organelle-specific proteins. The majority of chloroplast and mitochondrial proteins are specifically imported by the transit peptide and presequence, respectively. However, a significant number of proteins are also dually targeted to these two organelles. Currently, it is not fully understood how proteins are dually targeted to both chloroplasts and mitochondria. In this study, the mechanism underlying mitochondrial targeting of dual targeting AtSufE1 in Arabidopsis was elucidated. The N-terminal fragment containing 80 residues of AtSufE1 (AtSufE1N80) was sufficient to confer dual targeting of reporter protein, AtSufE1N80:GFP, in protoplasts. Two sequence motifs, two arginine residues at 15th and 21st positions, and amino acid (aa) sequence motif AKTLLLRPLK from the 31st to 40th aa position, were responsible for targeting to mitochondria a portion of reporter proteins amid the chloroplast targeting. The sequence motif PSEVPFRRT from the 41st to 50th aa position constitutes a common motif for targeting to both chloroplasts and mitochondria. For mitochondrial import of AtSufE1:N80, Metaxin played a critical role. In addition, BiFC and protein pull-down experiments showed that AtSufE1N80 specifically interacts with import receptors, Metaxin and Tom20. The interaction of AtSufE1N80 with Metaxin was required for the interaction with Tom20. Based on these results, we propose that mitochondrial targeting of dual-targeting AtSufE1 is mediated by both mitochondria-specific and common sequence motifs in the signal sequence through the interaction with import receptors, Metaxin and Tom20, in a successive manner.

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