Binds phosphatidylcholine, phosphatidylinositol, polychlorinated biphenyls (PCB) and weakly progesterone, potent inhibitor of phospholipase A2. Antiparallel homodimer; disulfide-linked (By similarity). Interaction with LMBR1L is controversial (By similarity). Clara cells (nonciliated cells of the surface epithelium of the pulmonary airways). Belongs to the secretoglobin family.