What kinds of amino acids on histone tails are able to be phosphorylated and why?
Also, how would this affect the connection of DNA and the histones?
To identify the types of amino acids on histone tails that can be phosphorylated, we need to look at the structure and composition of histones. Histones are proteins that play a critical role in DNA packaging and gene regulation. The tails of histones protrude from the nucleosome core and can undergo various post-translational modifications, including phosphorylation.
Histone tails consist of a series of amino acids linked together. The amino acids commonly found in histone tails are lysine (K), arginine (R), serine (S), threonine (T), and tyrosine (Y). Among these, lysine, serine, and threonine residues are frequently targeted for phosphorylation.
Phosphorylation is the addition of a phosphate group (PO4) to a specific amino acid on a protein. The enzymes responsible for phosphorylating histone tails are called kinases. Phosphorylation events can occur on the hydroxyl (-OH) groups of serine and threonine residues, as well as on the amino groups of lysine residues.
The presence of a hydroxyl group (-OH) on serine and threonine makes them ideal phosphorylation targets because kinases can easily transfer a phosphate group to these amino acids through phosphoester bond formation. As for lysine residues, their amino groups can also be targeted for phosphorylation, though it is less common compared to serine and threonine.
The phosphorylation of histone tails plays a crucial role in regulating chromatin structure and gene expression. It can influence interactions with other proteins and modulate the accessibility of DNA, thereby affecting various cellular processes, including transcription, DNA repair, and cell signaling.
In summary, the amino acids most commonly targeted for phosphorylation on histone tails are serine, threonine, and lysine. The presence of hydroxyl groups on serine and threonine and the amino group on lysine makes them suitable phosphorylation sites for kinases. This phosphorylation plays a key role in regulating gene expression and chromatin dynamics.