Problem 11, 130C

Problem 11, 130C - b) In mammals, the methylation of arg...

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Problem 11 (Due May 21 st ) In order to modify chromatin structure so as to facilitate or inhibit transcription of DNA, histones in resident nucleosomes are modified by acetylation, phosphorylation and methylation of lys and arg residues. When the transcriptional requirements of the cell are altered so that a different set of genes need to be expressed, the former modifications have to be removed to reestablish the original configuration of the chromatin. a) What roles does each of the above modifications play in promoting or inhibiting access to DNA?
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Unformatted text preview: b) In mammals, the methylation of arg residues is reversed by peptidylarginine deaminases. The reaction catalyzed by these enzymes produces a citrulline at the site of modification instead of unmethylated arginine. Specify the other product formed by the deaminase catalyzed reaction, suggest a mechanism for the transformation and stipulate the subsequent reactions that restore the side-chain to its original unmethylated form. (Hint: consider amino acid biosynthesis.)...
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