35 kDa pulmonary surfactant-associated protein,alveolar proteinosis protein,COLEC5,collectin 5,Collectin-5,PSAP,PSPA,PSP-A,pulmonary surfactant-associated protein A2,SFTP1,SFTPA2B,SP-2A,SP-A,SPA2,SPAII,surfactant, pulmonary-associated protein A2A.
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.