SFTPA2-In presence of calcium ions; it binds to surfactant phospholipids and contributes to lower the surface tension at the air-liquid interface in the alveoli of the mammalian lung and is essential for normal respiration. SFTPA1-his gene encodes a lung surfactant protein that is a member of a subfamily of C-type lectins called collectins. The encoded protein binds specific carbohydrate moieties found on lipids and on the surface of microorganisms. This protein plays an essential role in surfactant homeostasis and in the defense against respiratory pathogens. Mutations in this gene are associated with idiopathic pulmonary fibrosis. Alternate splicing results in multiple transcript variants.