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Sequence homologies among bacterial and mitochondrial superoxide dismutases
Summary
Amino-terminal sequencing of superoxide dismutases reveals homology among mitochondrial and bacterial enzymes, supporting endosymbiotic theory. Eukaryotic copper-zinc enzymes are distinct from manganese enzymes.
Area of Science:
- Biochemistry
- Molecular Biology
- Evolutionary Biology
Background:
- Superoxide dismutases (SODs) are critical enzymes protecting cells from oxidative stress.
- Mitochondrial SODs and bacterial SODs share functional similarities.
- Understanding SOD evolution provides insights into cellular origins.
Purpose of the Study:
- To investigate the evolutionary relationships between different types of superoxide dismutases.
- To analyze the amino-terminal sequences of manganese and iron-containing SODs.
- To compare these sequences with eukaryotic copper-zinc SODs.
Main Methods:
- Automated Edman degradation was used for amino-terminal sequencing.
- Sequences from chicken-liver mitochondria, Escherichia coli (manganese and iron enzymes), and bovine erythrocytes were analyzed.
- Homology analysis was performed on the obtained amino-terminal sequences.
Main Results:
- High homology was found among the amino-terminal sequences of chicken mitochondrial SOD, E. coli manganese SOD, and E. coli iron SOD.
- These homologies support the known structural and functional similarities of these enzymes.
- No significant homology was observed between these manganese/iron enzymes and bovine erythrocyte copper-zinc SOD.
Conclusions:
- The observed homology provides further evidence for the endosymbiotic origin of mitochondria.
- The distinctness of copper-zinc SODs from manganese SODs is supported at the sequence level.
- This classification aligns with differences in stability and catalytic properties between these SOD families.