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New insights into the co-evolution of cytochrome c reductase and the mitochondrial processing peptidase
S Brumme1, V Kruft, U K Schmitz
1Institut für Angewandte Genetik, Universität Hannover, Herrenhäuser Strasse 2, 30419 Hannover, Germany.
Abstract:
The mitochondrial processing peptidase (MPP) is a heterodimeric enzyme that forms part of the cytochrome c reductase complex from higher plants. Mitochondria from mammals and yeast contain two homologous enzymes: (i) an active MPP within the mitochondrial matrix and (ii) an inactive MPP within the cytochrome c reductase complex. To elucidate the evolution of MPP, the cytochrome c reductase complexes from lower plants were isolated and tested for processing activity. Mitochondria were prepared from the staghorn fern Platycerium bifurcatum, from the horsetail Equisetum arvense, and from the colorless algae Polytomella, and cytochrome c reductase complexes were purified by a micro-isolation procedure based on Blue-native polyacrylamide gel electrophoresis and electroelution. This is the first report on the subunit composition of a respiratory enzyme complex from a fern or a horsetail. The cytochrome c reductase complexes from P. bifurcatum and E. arvense are shown to efficiently process mitochondrial precursor proteins, whereas the enzyme complex from Polytomella lacks proteolytic activity. An evolutionary model is suggested that assumes a correlation between the presence of an active MPP within the cytochrome c reductase complex and the occurrence of chloroplasts.
Insights
Mitochondrial processing peptidase (MPP) in lower plants shows active processing in ferns and horsetails but not algae. This suggests an evolutionary link between active MPP in respiratory complexes and the presence of chloroplasts.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Plant Science
Background:
- Mitochondrial processing peptidase (MPP) is a key enzyme in protein processing.
- Higher plants possess MPP in both the mitochondrial matrix and the cytochrome c reductase complex.
- Mammals and yeast have distinct active and inactive MPP forms.
Purpose of the Study:
- To investigate the evolutionary history of MPP.
- To determine the processing activity of cytochrome c reductase complexes in lower plants.
- To correlate MPP activity with the presence of chloroplasts.
Main Methods:
- Isolation and purification of cytochrome c reductase complexes from Platycerium bifurcatum (fern), Equisetum arvense (horsetail), and Polytomella (algae).
- Analysis of subunit composition of respiratory enzyme complexes.
- Assay of proteolytic activity of isolated complexes.
Main Results:
- Cytochrome c reductase complexes from P. bifurcatum and E. arvense demonstrated efficient processing of mitochondrial precursor proteins.
- The enzyme complex from Polytomella lacked proteolytic activity.
- This study provides the first report on respiratory enzyme complex composition from fern and horsetail.
Conclusions:
- The presence of active MPP within the cytochrome c reductase complex is linked to the evolutionary history of plants.
- An evolutionary model suggests a correlation between active MPP in respiratory complexes and the presence of chloroplasts.
- Lower plants exhibit diverse MPP functionalities within their respiratory enzyme complexes.