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. Enhances the expression of MYO18A/SP-R210 on alveolar macrophages (By similarity).
(Microbial infection) Recognition of M.tuberculosis by dendritic cells may occur partially via this molecule (, ). Can recognize, bind, and opsonize pathogens to enhance their elimination by alveolar macrophages .
(Microbial infection) Binds M.pneumoniae CARDS toxin, serves as one receptor for this pathogen (, ). When SFTPA1 is down-regulated by siRNA, less toxin binds to human cells and less vacuolization (a symptom of M.pneumoniae infection) is seen .
Subcellular locations: Secreted, Secreted, Extracellular space, Extracellular matrix, Secreted, Extracellular space, Surface film