Binds phosphatidylcholine, phosphatidylinositol, polychlorinated biphenyls (PCB) and weakly progesterone, potent inhibitor of phospholipase A2. Antiparallel homodimer; disulfide-linked (PubMed:7664082). Interaction with LMBR1L has been observed in PubMed:16423471, but not in PubMed:23964685 (PubMed:16423471, PubMed:23964685). Clara cells (nonciliated cells of the surface epithelium of the pulmonary airways). Belongs to the secretoglobin family.