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A cytochrome c methyltransferase from Crithidia oncopelti
The Biochemical Journal
|February 1, 1982
Summary
Methylation of Crithidia cytochrome c-557 occurs at specific lysine and proline residues. This unique methyltransferase enzyme methylates its substrate more efficiently than yeast or Neurospora enzymes.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Mitochondrial cytochrome c-557 in Crithidia oncopelti is methylated in vivo.
- Methylation involves lysine and N-terminal proline residues, utilizing methionine's methyl group.
Purpose of the Study:
- To investigate the methyltransferase activity in Crithidia oncopelti cell extracts.
- To characterize the substrate specificity and efficiency of the Crithidia methyltransferase.
Main Methods:
- Purification of Crithidia cytochrome c-557.
- Assay of methyltransferase activity using S-adenosylmethionine as the methyl donor.
- Radioactive labeling with [14C]methyl groups to identify methylation sites.
Main Results:
- Crithidia cytochrome c-557 is an excellent substrate for the endogenous methyltransferase, despite existing methylation.
- Methylation occurs specifically at lysine residue (-8) and the N-terminal proline residue.
- The Crithidia methyltransferase differs from yeast and Neurospora enzymes, showing higher stability and methylation completion.
Conclusions:
- Crithidia oncopelti possesses a distinct methyltransferase system for its cytochrome c-557.
- This enzyme exhibits unique substrate acceptance and methylation efficiency compared to other known systems.