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Import of a mitochondrial presequence into P. denitrificans. Insight into the evolution of protein transport
1Department of Chemistry, University of California at San Diego, La Jolla 92093-0506.
Abstract:
According to the endosymbiont hypothesis, mitochondria are descended from ancient aerobic bacteria that were engulfed by protoeukaryotic cells. Experiments described here show that a synthetic peptide corresponding to a yeast mitochondrial targeting sequence can be imported into Paracoccus denitrificans, a soil bacterium thought to be closely related to the protomitochondrion. The import is very similar to that observed with isolated yeast mitochondria. The results suggest that the protomitochondrion may have been inherently able to translocate mitochondrial presequences. This ability may partly explain the development of the protein import process during the evolution of the mitochondrion.
Insights
Mitochondria may have evolved from bacteria, and experiments show yeast mitochondrial targeting sequences can enter related bacteria. This suggests early mitochondria could import proteins, aiding their evolutionary development.
Area of Science:
- Evolutionary biology
- Cell biology
- Mitochondrial biogenesis
Background:
- The endosymbiont hypothesis posits mitochondria originated from engulfed aerobic bacteria.
- Understanding early mitochondrial protein import mechanisms is crucial for evolutionary studies.
Purpose of the Study:
- To investigate if ancient bacteria, like Paracoccus denitrificans, could import mitochondrial targeting sequences.
- To explore the evolutionary origins of mitochondrial protein translocation.
Main Methods:
- Synthesized a peptide with a yeast mitochondrial targeting sequence.
- Introduced the peptide into Paracoccus denitrificans.
- Compared the import process to that in isolated yeast mitochondria.
Main Results:
- The synthetic peptide was successfully imported into Paracoccus denitrificans.
- The import mechanism closely resembled that of yeast mitochondria.
- This indicates inherent protein translocation capabilities in early mitochondria.
Conclusions:
- Protomitochondria likely possessed intrinsic protein translocation abilities.
- This inherent ability may have been key to developing the complex mitochondrial protein import system.
- Supports the endosymbiotic origin of mitochondria and their functional integration.