Protein translocation channel of mitochondrial inner membrane and matrix-exposed import motor communicate via two-domain coupling protein

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Abstract

The majority of mitochondrial proteins are targeted to mitochondria by N-terminal presequences and use the TIM23 complex for their translocation across the mitochondrial inner membrane. During import, translocation through the channel in the inner membrane is coupled to the ATP-dependent action of an Hsp70-based import motor at the matrix face. How these two processes are coordinated remained unclear. We show here that the two domain structure of Tim44 plays a central role in this process. The N-terminal domain of Tim44 interacts with the components of the import motor whereas its C-terminal domain interacts with the translocation channel and is in contact with translocating proteins. Our data suggest that the translocation channel and the import motor of the TIM23 complex communicate through rearrangements of the two domains of Tim44 that are stimulated by translocating proteins.

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Rupa Banerjee

Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany

Competing interests
The authors declare that no competing interests exist.
Christina Gladkova

Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany

Competing interests
The authors declare that no competing interests exist.
Koyeli Mapa

Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany

Competing interests
The authors declare that no competing interests exist.
Gregor Witte

Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany

Competing interests
The authors declare that no competing interests exist.
Dejana Mokranjac

Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany

For correspondence
dejana.mokranjac@med.uni-muenchen.de

Competing interests
The authors declare that no competing interests exist.

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