Cholesterol-binding protein involved in the redistribution of cholesterol from lipid droplets to the endoplasmic reticulum (PubMed:19729679, PubMed:32358067). Required to meet cholesterol demands during erythropoietic differentiation (PubMed:19729679, PubMed:32358067). May play a role in transport processes at the plasma membrane of erythrocytes, including regulating VDAC-mediated ATP export, and import of the heme precursors protoporphyrin IX and 5-aminolevulinic acid (By similarity). Homotetramer. May also form homodimer. Localizes to the plasma membrane and intracellular membranes in developing and mature erythrocytes. Expressed in liver, bone marrow and spleen. In spleen, detected in red pulp but not in white pulp. Not expressed at 10.5 dpc. First detected at 12.5 dpc in the primordial liver (PubMed:19729679). Increased hepatic levels are found at 15.5 dpc followed by decline throughout newborn stage P1 and postnatal stages P5 and P10 with no hepatic expression in the adult (PubMed:19729679). In bone marrow, expressed during late gestation stages and remains elevated until adulthood (PubMed:19729679). In newborn and adult mice, also expressed in spleen (PubMed:19729679). The C-terminal region mediates cholesterol-binding. Decreases erythrocyte count and increases reticulocyte count (PubMed:32358067). Abnormal erythroblast cytokinesis and differentiation (PubMed:32358067). Decreases hemoglobin levels in maturing erythroid cells (PubMed:32358067). Belongs to the TspO/BZRP family.