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Tom70 enhances mitochondrial preprotein import efficiency by binding to internal targeting sequences
Sandra Backes1, Steffen Hess1, Felix Boos1
1Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany.
The Journal of Cell Biology
|February 1, 2018
Summary
Mitochondrial protein import relies on internal signals (iMTS-Ls) that bind to Tom70. These signals enhance protein translocation into mitochondria, especially for proteins with high iMTS-L content.
Area of Science:
- Cell Biology
- Mitochondrial Biogenesis
- Protein Import Mechanisms
Background:
- Mitochondrial biogenesis requires importing hundreds of preproteins.
- N-terminal matrix-targeting signals (MTSs) guide preproteins to surface receptors like Tom20, Tom22, and Tom70.
Purpose of the Study:
- To investigate the role of internal MTS-like signals (iMTS-Ls) in preprotein import.
- To determine the contribution of iMTS-Ls to mitochondrial targeting and translocation.
Main Methods:
- In silico prediction of iMTS-Ls based on their characteristic properties.
- Experimental validation using Atp1 as a model substrate.
- Analysis of preprotein import in the presence and absence of Tom70.
Main Results:
- Many preproteins possess iMTS-Ls in their mature regions, sharing properties with N-terminal presequences.
- iMTS-Ls mediate binding to the Tom70 receptor.
- Preproteins with high iMTS-L content show significantly impaired import without Tom70.
Conclusions:
- iMTS-Ls are functional signals that contribute to mitochondrial protein import.
- A 'stepping stone' model is proposed where Tom70-mediated interactions with iMTS-Ls enhance import efficiency.
- Tom70 plays a crucial role in importing preproteins with significant iMTS-L content.
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