Phospholipid transfer protein that preferentially selects lipid species containing a palmitoyl or stearoyl chain on the sn-1 and an unsaturated fatty acyl chain (18:1 or 18:2) on the sn-2 position. Able to transfer phosphatidylcholine (PC) and phosphatidyetanolamline (PE) between membranes (By similarity). May play metabolic roles in sperm maturation or fertilization. Mainly cytosolic (By similarity). In testis was predominantly detected at the flagella of elongated spermatids, with a strong signal also found at the tail of epididymal sperm. Testis, kidney, liver, and intestine with the highest level in the testis. During male germ cell development, it was detected first in the 23-day-old mouse testis, and the signal increased with age. Phosphorylation at Ser-284 by CK2 negatively regulates lipid transfer activity, possibly by decreasing membrane association.