Essential for sperm motility and male fertility (PubMed:26265198). Plays an important role in sperm motility by regulating the organization and function of the mitochondria and is also required for correct sperm midpiece assembly (PubMed:26265198). Localizes to the midpiece of the sperm flagellum. Expressed specifically in adult testis (at protein level). Male mice are infertile, their sperms exhibit disorganized mitochondrial structure and the sperm-abundance of mitochondrial proteins and activities of mitochondrial respiratory chain complex IV, and ATP levels are significantly reduced (PubMed:26265198). Epididymal sperm possess seriously disrupted midpieces, leading to a severe reduction in sperm motility and infertility (PubMed:26265198).