Editing Histone octamer (section)

{{short description|8-protein complex forming the core of nucleosomes}}
[[File:Basic units of chromatin structure.svg|thumb|Basic units of [[chromatin]] structure]]

In [[molecular biology]], a '''histone octamer''' is the eight-protein [[Protein complex|complex]] found at the center of a [[nucleosome|nucleosome core particle]]. It consists of two copies of each of the four core [[histone]] proteins ([[Histone H2A|H2A]], [[Histone H2B|H2B]], [[Histone H3|H3]], and [[Histone H4|H4]]). The octamer assembles when a [[tetramer]], containing two copies of H3 and two of H4, complexes with two H2A/H2B dimers. Each histone has both an [[N-terminus|N-terminal]] tail and a [[C-terminus|C-terminal]] histone-fold. Each of these key components interacts with [[DNA]] in its own way through a series of weak interactions, including [[hydrogen bond]]s and [[Salt bridge (protein and supramolecular)|salt bridge]]s. These interactions keep the DNA and the histone octamer loosely associated, and ultimately allow the two to re-position or to separate entirely.