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A neutral metallo endoprotease involved in the processing of an F1-ATPase subunit precursor in mitochondria
Abstract:
A post-translational processing assay of the precursor to the yeast F1-ATPase subunit has been utilized to examine a mitochondrial endoprotease which cleaves this subunit precursor to the size of a mature subunit. The endoprotease is extracted from purified mitochondria as a soluble complex of Mr = 115,000 which is composed of subunits of lower molecular weight when examined on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It exhibits a pH optimum of between pH 7 and 8 and is inactive at pH 6.5 and below. The mitochondrial endoprotease is insensitive to serine esterase inhibitors, but is inhibited by EDTA and o-phenanthroline. Restoration of precursor subunit processing activity in the presence of metal chelators is strictly dependent on excess Co2+ and Mn2+ over other heavy metals examined. These and additional data indicate that this soluble metallo endoprotease is involved in the processing of other cytoplasmically synthesized precursor subunits of the ATPase complex in addition to the subunit 2 precursor. The role of this processing enzyme in the assembly of mitochondrial inner membrane complexes is discussed in light of the current model of mitochondrial biogenesis.
Insights
Researchers identified a soluble metallo endoprotease in yeast mitochondria that processes F1-ATPase subunit precursors. This enzyme is crucial for assembling mitochondrial inner membrane complexes.
Area of Science:
- Mitochondrial biogenesis
- Protein processing
- Enzyme kinetics
Background:
- The F1-ATPase is a key enzyme complex in mitochondrial ATP synthesis.
- Post-translational modification is essential for the proper assembly and function of mitochondrial proteins.
Purpose of the Study:
- To characterize a mitochondrial endoprotease responsible for processing yeast F1-ATPase subunit precursors.
- To elucidate the enzymatic properties and cofactor requirements of this endoprotease.
Main Methods:
- Utilized a post-translational processing assay with yeast F1-ATPase subunit precursor.
- Extracted and purified the endoprotease from mitochondria.
- Determined enzyme activity across a pH range and assessed inhibition by various agents.
- Investigated cofactor dependency using metal chelators and specific ions.
Main Results:
- Identified a soluble mitochondrial endoprotease complex (Mr = 115,000) with a pH optimum between 7 and 8.
- The enzyme is inhibited by EDTA and o-phenanthroline, indicating it is a metalloendoprotease.
- Enzyme activity is restored by Co2+ and Mn2+, suggesting these as essential cofactors.
- The endoprotease processes F1-ATPase subunit 2 precursor and likely other cytoplasmic-synthesized precursors.
Conclusions:
- The characterized soluble metalloendoprotease plays a significant role in the post-translational processing of yeast F1-ATPase subunits.
- This enzyme is vital for the correct assembly of mitochondrial inner membrane complexes.
- Understanding this processing enzyme contributes to the broader model of mitochondrial biogenesis.