HBS1L (HBS1-like), also known as EF-1a or ERFS, is a 684 amino acid protein that belongs to the GTP-binding elongation factor family and exists as multiple alternatively spliced isoforms. Expressed in kidney, brain, heart, placenta, liver, muscle and pancreas, HSB1L is thought to play a role in controlling fetal hemoglobin levels, specifically influencing platelet, monocyte and erythrocyte hemoglobin content. The gene encoding HBS1L maps to a locus on human chromosome 6 that is associated with sickle cell anemia and beta-thalassemia, suggesting a role for HBS1L in the pathogenesis of blood disorders.