Binds and compacts DNA (about 120 base pairs per nucleosome, corresponding to four histone dimers) to form nucleosome-like structures. Homodimer or heterodimer. Dimers then assemble into higher oligomers, with the DNA wrapped around the protein core. Higher order oligomerization of these structures can give rise to long, superhelical fibers (in vitro). Belongs to the archaeal histone HMF family.