Pulmonary surfactant consists of a complex mixture of phospholipids and several proteins essential to normal respiratory function. Surfactant proteins SP-B (SFTPB) (MIM.178640) and SP-C (SFTPC) (MIM.178620) and the surfactant lipids are involved in the reduction of surface tension at the air-liquid barrier in the alveoli of the lung, whereas the surfactant protein SP-A (SFTPA1 and SFTPA2) (MIM.178630) and SP-D (SFTPD) appear to contribute to local immune defense by mediating phagocytosis.
SP-D was identified in lung lavage by its similarity to rat SP-D in both its molecular mass and its Ca(2+)-dependent-binding affinity for maltose.
A high concentration of glycine (22%), hydroxyproline, and hydroxylysine in the amino acid composition of SP-D indicated that it contained a collagen-like structure.
Collagenase digestion yielded a 20-kD collagenase-resistant globular fragment that retained affinity for maltose.
See also
SFTPs
surfactant