Acts as an ADP-ribosylating toxin, which may transfer the ADP-ribosyl group from NAD(+) to specific amino acids in target proteins. Elicits cytopathic effects in mammalian cells, such as disorganization and disruption of respiratory epithelial integrity in tracheal epithelium and vacuolization in the cytoplasm of CHO and HeLa cells. Binds to the pulmonary surfactant-associated protein A (SFTPA/SP-A), the major mammalian protein component of pulmonary surfactant. Surface-associated protein. Belongs to the bacterial exotoxin subunit A family.