Related Experiment Videos
Tom7 modulates the dynamics of the mitochondrial outer membrane translocase and plays a pathway-related role in
A Hönlinger1, U Bömer, A Alconada
1Institut für Biochemie und Molekularbiologie, Universität Freiburg, Martinsried, Germany.
Abstract:
The preprotein translocase of the outer mitochondrial membrane is a multi-subunit complex with receptors and a general import pore. We report the molecular identification of Tom7, a small subunit of the translocase that behaves as an integral membrane protein. The deletion of TOM7 inhibited the mitochondrial import of the outer membrane protein porin, whereas the import of preproteins destined for the mitochondrial interior was impaired only slightly. However, protein import into the mitochondrial interior was strongly inhibited when it occurred in two steps: preprotein accumulation at the outer membrane in the absence of a membrane potential and subsequent further import after the re-establishment of a membrane potential. The delay of protein import into tom7delta mitochondria seemed to occur after the binding of preproteins to the outer membrane receptor sites. A lack of Tom7 stabilized the interaction between the receptors Tom20 and Tom22 and the import pore component Tom40. This indicated that Tom7 exerts a destabilizing effect on part of the outer membrane translocase, whereas Tom6 stabilizes the interaction between the receptors and the import pore. Synthetic growth defects of the double mutants tom7delta tom20delta and tom7delta tom6delta provided genetic evidence for the functional relationship of Tom7 with Tom20 and Tom6. These results suggest that (i) Tom7 plays a role in sorting and accumulation of the preproteins at the outer membrane, and (ii) Tom7 and Tom6 perform complementary functions in modulating the dynamics of the outer membrane translocase.
Insights
Tom7, a mitochondrial outer membrane protein, is crucial for efficient protein import into mitochondria. Its absence disrupts preprotein sorting and accumulation, affecting mitochondrial function.
Area of Science:
- Mitochondrial biology
- Protein translocation
- Molecular cell biology
Background:
- The outer mitochondrial membrane contains a preprotein translocase complex responsible for protein import.
- This complex includes receptors and a general import pore, but its precise regulation is not fully understood.
Purpose of the Study:
- To identify and characterize the role of Tom7, a small subunit of the mitochondrial preprotein translocase.
- To elucidate the function of Tom7 in the process of protein import into mitochondria.
Main Methods:
- Molecular identification of Tom7 as an integral membrane protein.
- Analysis of mitochondrial protein import in tom7 deletion mutants (tom7Δ).
- Genetic analysis using double mutants (e.g., tom7Δ tom20Δ, tom7Δ tom6Δ).
Main Results:
- Deletion of TOM7 specifically inhibited the import of outer membrane proteins like porin.
- Protein import into the mitochondrial interior was impaired, particularly in a two-step import process involving preprotein accumulation.
- Lack of Tom7 stabilized interactions within the translocase complex, suggesting a destabilizing role for Tom7.
- Tom7 and Tom6 were found to have complementary functions in regulating the translocase dynamics.
Conclusions:
- Tom7 plays a significant role in the sorting and accumulation of preproteins at the outer mitochondrial membrane.
- Tom7 and Tom6 work together to modulate the dynamic interactions within the outer mitochondrial translocase complex.
- Understanding Tom7's function provides insights into the regulation of mitochondrial protein import.