The Histone H2A residues 1 to 20 are derived from histone 2A (H2A) which is one of the four core histones (H2A, H2B, H3 and H4) fundamental in compacting eukaryotic DNA into a structure known as the nucleosome. The nucleosome arises when 147 base pairs of DNA wrap around a H3-H4 tetramer and two H2A-H2B dimers, forming the histone octamer core.

At the site of DNA entry on the outer nucleosome, the C-terminus of H2A is present and is able to interact with linker histones or other factors. This allows for variation and changes in nucleosome stability to occur. Furthermore Histone H2A has histone variants such as H2A.Z and H2A.X (which are present in all organisms) and these variants alter the organisation of the DNA.

Due to histones containing a large number of lysine and arginine residues they have a positive net charge which interacts in an electrostatic manner with the negatively charged phosphate groups in DNA. The transcriptional activation or silencing of the chromatin is controlled by ATP-dependent chromatin remodelling factors and histone modifying enzymes which target histone proteins. Both processes function to alter to change the positioning of the nucleosome, allowing the DNA it to be either available to the transcription machinery or inaccessible.

Biotin has been added to the lysine on GGK.