21. Histone deacetylase (HDAC) catalyses the removal of acetyl group from N-terminal of histones. Which amino acid of histone is involved in this process?
(1) Lysine (2) Arginine
(3) Asparagine (4) Histidine
Histone acetylation and deacetylation are critical post-translational modifications that regulate chromatin structure and gene expression. Histone deacetylases (HDACs) catalyze the removal of acetyl groups from specific amino acids on histones, primarily lysine residues. This article explains why lysine is the key target of HDACs and how this modification affects chromatin dynamics.
Lysine Acetylation and Deacetylation
Lysine residues in the N-terminal tails of core histones carry a positive charge that facilitates tight binding to the negatively charged DNA backbone. Acetylation of lysine neutralizes this charge, loosening chromatin and enabling transcription.
HDACs reverse this modification by removing acetyl groups from the ε-amino group of lysine, restoring the positive charge and promoting chromatin condensation and transcriptional repression.
Specificity of HDACs for Lysine
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HDACs specifically recognize acetylated lysine residues.
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Other amino acids such as arginine, asparagine, or histidine are not acetylated in histones and thus are not substrates for HDACs.
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This specificity is crucial for precise regulation of gene expression.
Biological Implications
By targeting lysine residues, HDACs play essential roles in:
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Gene silencing
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Cell cycle regulation
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Development and differentiation
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Disease processes including cancer
Conclusion
The amino acid lysine in histone tails is the specific substrate for histone deacetylases. Removal of acetyl groups from lysine residues by HDACs modulates chromatin structure and regulates gene expression.
Answer:
(1) Lysine
