Promotes cholesterol efflux from sperm which renders sperm capable of fertilization (PubMed:22237709). Has also been shown to decrease levels of intracellular esterified neutral lipids including cholesteryl esters, fatty acid esters and triacylglycerols (PubMed:15810880). ATP + cholesterol(in) + H2O = ADP + cholesterol(out) + H(+) + phosphate In the testis, detected predominantly in elongated spermatids at the late stage of germ cell development and in sperm, with no expression detected in immature germ cells such as spermatogonia and spermatocytes or in somatic cells such as Sertoli cells (at protein level) (PubMed:15810880). Expressed in the head and tail midpiece of elongated spermatids and sperm (at protein level) (PubMed:22237709). Expressed exclusively in the testis (PubMed:15810880, PubMed:22237709). Detected in the testis at low levels at postnatal day 5 but increases at postnatal days 20 and 45 (at protein level). N-glycosylated. Belongs to the ABC transporter superfamily. ABCA family.