Protamine-P3 family consists of protamine 3 (PRM3) proteins. PRM3 proteins localize in the elongated spermatid cytoplasm (but not in mature sperm) and have been shown to affect sperm mobility [, ]. Despite their name, protamine, PRM3 proteins might not share the same function such as replacing somatic histones during spermiogenesis with other protamines [].