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Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
Published on: July 19, 2021
Cytochrome c methyltransferase, Ctm1p, of yeast
B Polevoda1, M R Martzen, B Das
1Department of Biochemistry and Biophysics, University of Rochester Medical School, Rochester, New York 14642, USA.
The Journal of Biological Chemistry
|May 3, 2000
Summary
Researchers identified Ctm1p as the enzyme responsible for trimethylating lysine 72 in yeast iso-1-cytochrome c. This specific methylation occurs in the cytosol on apocytochrome c, without affecting cell growth or protein function.
Area of Science:
- Biochemistry
- Molecular Biology
- Yeast Genetics
Background:
- Cytochromes c in plants and fungi possess methylated lysine residues, unlike those in higher animals.
- Previous screening identified YHR109w as potentially involved in methylating horse cytochrome c.
Purpose of the Study:
- To identify and characterize the specific enzyme responsible for trimethylating lysine 72 of iso-1-cytochrome c in Saccharomyces cerevisiae.
- To investigate the substrate specificity and cellular localization of the identified methyltransferase.
Main Methods:
- Screening of Saccharomyces cerevisiae strains overproducing open reading frames fused to glutathione S-transferase.
- In vitro methylation assays using purified Ctm1p and various substrates.
- Analysis of cytochrome c methylation in wild-type, ctm1-Delta, and K72R mutant strains.
Main Results:
- Ctm1p was identified as the specific enzyme responsible for trimethylating lysine 72 of iso-1-cytochrome c.
- Ctm1p methylates unmethylated cytochrome c in vitro, with specificity for apocytochrome c over holocytochrome c, proteins, or nucleic acids.
- The ctm1-Delta strain showed no growth defects, and the unmethylated iso-1-cytochrome c retained normal activity.
Conclusions:
- Ctm1p is the dedicated methyltransferase for lysine 72 trimethylation of iso-1-cytochrome c in yeast.
- The enzyme acts on the cytosolic substrate apocytochrome c.
- Ctm1p and cytochrome c expression are coordinately regulated, suggesting co-evolution for this specific post-translational modification.
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