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Interaction with mitochondrial membranes of a synthetic peptide with a sequence common to extra peptides of
Abstract:
A hepta-peptide, Arg-Leu-Leu-Pro-Ser-Leu-Gly, which has a sequence involved in the extra peptides of mitochondrial proteins, was synthesized chemically. The peptide was found to bind specifically to mitochondria, but not to microsomes. The binding was blocked by pretreatment of mitochondria with trypsin but was not affected by the presence of apocytochrome c. The synthetic peptide inhibited the binding to mitochondria of the precursor protein of ATPase inhibitor, which was synthesized in vitro, but did not inhibit that of the precursor of the 9 K stabilizing factor, which has an entirely different extra-peptide sequence. The peptide also did not inhibit the binding of apocytochrome c. These results suggest the existence of a common protein receptor on mitochondrial membranes that facilitates entrance of a group of mitochondrial precursor proteins, including pre-ATPase inhibitor.
Insights
A synthetic peptide, Arg-Leu-Leu-Pro-Ser-Leu-Gly, specifically binds to mitochondria. This peptide inhibits the entry of certain mitochondrial precursor proteins, suggesting a common mitochondrial receptor.
Area of Science:
- Mitochondrial biology
- Protein import mechanisms
- Molecular cell biology
Background:
- Mitochondrial proteins are synthesized in the cytoplasm and imported into mitochondria.
- Specific sequences on these precursor proteins target them to mitochondria.
- The precise mechanisms and receptors involved in protein import are not fully understood.
Purpose of the Study:
- To synthesize a specific hepta-peptide (Arg-Leu-Leu-Pro-Ser-Leu-Gly) involved in mitochondrial protein targeting.
- To investigate the binding characteristics of this peptide to cellular organelles.
- To determine if this peptide plays a role in the import of mitochondrial precursor proteins.
Main Methods:
- Chemical synthesis of the hepta-peptide Arg-Leu-Leu-Pro-Ser-Leu-Gly.
- Binding assays using isolated mitochondria and microsomes.
- Inhibition studies using in vitro synthesized precursor proteins (pre-ATPase inhibitor, 9 K stabilizing factor) and apocytochrome c.
- Mitochondrial pretreatment with trypsin to assess receptor involvement.
Main Results:
- The synthetic peptide specifically bound to mitochondria, not microsomes.
- Mitochondrial binding of the peptide was abolished by trypsin pretreatment.
- The peptide inhibited the mitochondrial binding of pre-ATPase inhibitor precursor but not the 9 K stabilizing factor precursor.
- Apocytochrome c binding was unaffected by the peptide.
Conclusions:
- A common protein receptor exists on mitochondrial membranes.
- This receptor facilitates the entry of specific mitochondrial precursor proteins, such as pre-ATPase inhibitor.
- The hepta-peptide acts as a ligand for this mitochondrial import receptor.