These proteins fold into a motif that looks like two people shaking hands.
Acid-urea gels are mainly used to fractionate these proteins. These proteins fold into a motif that looks like two people shaking hands. Post-translational modifications labelled K9 and K27 occur on this class of proteins, which are covalently modified by Polycomb and Trithorax in  Drosophila . These proteins naturally exist as octamers containing two copies each of their sub-types numbered 2A, 2B, 3, and 4. Bromodomains specifically bind these proteins' (*)  tails. These proteins neutralize a surrounding negative charge since they're chock-full of arginines and lysines with positive charge. Methylation and acetylation of these nucleosomal proteins is key to epigenetic gene regulation. For 10 points, name these "beads" around which DNA wraps to form chromatin.
Acid-urea gels are mainly used to fractionate these proteins.
 histone s