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 [1, 2]. Prtl99C is a sperm chromatin-associated protein that is essential for male fertility [2].

1: Replacement by Drosophila melanogaster protamines and Mst77F of histones during chromatin condensation in late spermatids and role of sesame in the removal of these proteins from the male pronucleus. Jayaramaiah Raja S, Renkawitz-Pohl R; Mol Cell Biol. 2005;25:6165-6177. PMID:15988027

2: Prtl99C Acts Together with Protamines and Safeguards Male Fertility in Drosophila. Eren-Ghiani Z, Rathke C, Theofel I, Renkawitz-Pohl R; Cell Rep. 2015;13:2327-2335. PMID:26673329