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). Expressed in lung, uterus, and prostate. Belongs to the secretoglobin family.