This family consists of several insect proteins including protamine A (ProtA), protamine B (ProtB) and protamine-like protein 99C (Prtl99C) from Drosophila melanogaster. They contain a HMG-box and are involved in chromatin compaction during spermiogenesis. Prtl99C is a sperm chromatin-associated protein that is essential for male fertility.
Jiyao W et al.(2023). "The conserved domain database in 2023.",