Anti-Histone H1

Histone H1 is one of the 5 main histone proteins involved in the structure of chromatin in eukaryotic cells. A variant of the histone H1 protein is the histone H5, which has a similar structure and function, but is only found in avian erythrocytes, which unlike mammals have nuclei. Featuring a central globular domain and long C and N terminal tails H1 is involved with the packing of the 'beads on a string' structure into the '30nm solenoid' structure. H1 is present in half the amount of the other four histones. This is because unlike the other histones, H1 does not make up the nucleosome 'bead'. Instead, it sits on top of the structure, keeping in place the DNA that has wrapped around the nucleosome. Specifically, the H1 protein binds to the linker DNA (approximately 80 nucleotides in length) region between the histone beads, helping stabilize the zig-zagged 30nm chromatin fiber. H1 histone seals off the nucleosome at the location at which the linker DNA enters and leaves.