Nucleosome core particle contains how many histones?
Fundamental repeating unit revealed by micrococcal nuclease digestion is nucleosome core particle. High resolution crystallography shows 146 to 147 base pairs wrapped 1.65 left-handed superhelical turns around histone octamer disk. Octamer comprises two copies each of H2A, H2B, H3 and H4, totaling eight proteins organized as central H3-H4 tetramer flanked by two H2A-H2B dimers assembled via histone fold handshake motifs. This assembly induces negative supercoiling, reduces DNA length and provides stability through electrostatic contacts between arginine-rich histone surfaces and DNA phosphate
Ref: Luger et al., Nature 1997, 2.8 Å Nucleosome Core Particle Structure; NCBI Bookshelf, Chromosome Packaging
