BASIC TEMPLATE. “The HK97-fold, despite sequence, structural, and functional divergences, is a basic template for formation of a proteinacious shell utilized by viruses and prokaryotic cells alike. The protein shell, composed of HK97-like subunits, serves a protective role for the genomes of viruses infecting all three domains of life. Prokaryotic cells also utilize the HK97-fold to form encapsulin nanocompartments, and possibly gene transfer agent particles that contribute to high frequencies of horizontal gene transfer.”
http://www.sciencedirect.com/science/article/pii/S0042682215001920