Sperm protein required for fusion of sperm with the egg membrane during fertilization. Detected at the sperm head, equatorial region, neck and midpiece (at protein level) (PubMed:32210282). Expressed in testis (PubMed:24275887). Due to intron retention. Due to intron retention. Belongs to the SPACA6 family. Was originally thought to be a non protein-coding gene.