Structure and function of pulmonary surfactant proteins.

In summary, the isolation and characterization of three surfactant proteins have considerably changed our understanding of the nature of pulmonary surfactant and its metabolism. The isolation of the cDNAs and genes encoding the proteins and the elucidation of their structure now makes possible the generation of surfactant proteins for further study and for therapy of surfactant deficient states. Artificial surfactant consisting of appropriately modified human proteins can be produced by recombinant DNA technology. Mixed with appropriate synthetic phospholipids, these proteins may be useful for the treatment of infants with hyaline membrane disease. Significant progress has been made in identifying and characterizing these three more abundant proteins; however, many questions regarding the functions of numerous other proteins present in surfactant (whether produced by Type II cells, Type I cell, Clara cell, or others) remain unanswered. Knowledge of the factors controlling developmental expression of surfactant phospholipids and protein as well as the molecular basis of the interactions among the surfactant proteins and phospholipids may lead to new strategies for therapy of hyaline membrane disease. Major questions regarding the site and nature of posttranslational modification of the surfactant proteins, their sites of assembly with lipids, and their precise roles in the metabolism of surfactant in vitro remain to be clarified. It is hoped that answers to these questions will facilitate the identification and design of appropriate therapy of infants and adults with pulmonary disease associated with surfactant deficiency.