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Phosphodiester bonds between polypeptides and chromosomal DNA.
Journal of Molecular Biology
|February 25, 1983
Summary
Covalently bound polypeptides in DNA are resistant to proteases but can be released by chemical treatments. Phosphodiester bonds link these peptides to DNA, revealing a novel DNA-peptide complex.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Polypeptides co-purifying with DNA under alkaline conditions suggest a covalent linkage.
- Understanding DNA-protein interactions is crucial for various biological processes.
Purpose of the Study:
- To investigate the nature of the covalent bond between polypeptides and DNA.
- To characterize the protease-resistant DNA-peptide complex.
Main Methods:
- Radioiodination of tyrosine and histidine in co-purifying peptides.
- Sequential treatment with phenol, ethanol precipitation, and proteases (Proteinase K, Pronase).
- Chemical treatments including hot piperidine, strong acid, and formic acid/diphenylamine.
- Isolation and characterization of linking groups using phosphodiesterases.
Main Results:
- A significant portion of radioiodinated peptides remained associated with DNA after extensive protease digestion.
- This residual DNA-peptide complex was resistant to proteases but susceptible to harsh chemical treatments.
- Phosphodiesterases released peptides from isolated linking groups, indicating phosphodiester involvement.
Conclusions:
- A protease-resistant DNA-peptide complex exists, covalently linked via phosphodiester bonds.
- Harsh chemical treatments are required to break down this complex, highlighting its stability.
- This study elucidates a novel type of DNA modification involving covalently attached peptides.