Octameren

An octamer is an oligomeric assembly composed of eight subunits. In biochemistry and structural biology, octamers can be homomeric (eight identical subunits) or heteromeric (eight subunits of different types), and they can assemble into rings, disks, or compact globular complexes. The architecture often exhibits cyclic (C8) or dihedral (D4) symmetry, depending on the subunit interfaces.

Natural octamers are found in chromatin biology and other protein assemblies. The nucleosome core particle is a canonical example: it consists of two copies each of histones H2A, H2B, H3, and H4 forming a histone octamer that wraps about 147 base pairs of DNA.

Octamers also occur in various regulatory and structural complexes, and many octameric assemblies are formed by protein–protein interactions without covalent bonds. In addition to natural occurrences, octameric designs are created in protein engineering and nanotechnology to serve as scaffolds, cages, or functional units.

Because eight-subunit assemblies can provide stable, symmetric platforms for binding, catalysis, or cargo presentation, octamers are of interest in structural biology, biophysics, and bioengineering. See also terms such as oligomer, hexamer, and dodecamer for related assembly sizes and architectures.