Editing Histone octamer (section)

====Interactions with the minor groove====

The histone-fold domains’ interaction with the minor groove accounts for the majority of the interactions in the nucleosome.<ref name=luger>{{cite journal|last=Richmond|first=Timothy J.|author2=Luger, Karolin |author3=Mäder, Armin W. |author4=Richmond, Robin K. |author5= Sargent, David F. |journal=Nature|date=18 September 1997|volume=389|issue=6648|pages=251–260|doi=10.1038/38444|pmid=9305837 |title=Crystal structure of the nucleosome core particle at 2.8 A resolution|bibcode=1997Natur.389..251L|s2cid=4328827}}</ref> As the DNA wraps around the histone octamer, it exposes its minor groove to the histone octamer at 14 distinct locations. At these sites, the two interact through a series of weak, non-covalent bonds. The main source of bonds comes from hydrogen bonds, both direct and water-mediated.<ref name=andrews /> The histone-fold hydrogen bonds  with both phosphodiester backbone and the A:T rich bases. In these interactions, the histone fold binds to the oxygen atoms and [[hydroxyl]] side chains, respectively.<ref name=luger /> Together these sites have a total of about 40 hydrogen bonds, most of which are from the backbone interactions.<ref name=watson /> Additionally, 10 out of the 14 times that the minor groove faces the histone fold, an arginine side chain from the histone fold is inserted into the minor groove. The other four times, the arginine comes from a tail region of the histone.<ref name=luger />