Lipid-protein interactions of hydrophobic proteins SP-B and SP-C in lung surfactant assembly and dynamics

Phospholipids have the major role in pulmonary surfactant concerning its bi ophysical function of reducing surface tension at the alveolar air-liquid i nterface to facilitate respiratory mechanics. However, the presence of some specific, highs hydrophobic polypeptides is essential to modulate the phys ical behavior of phospholipids and to promote rapid formation of stable sur face films that are able to produce surface tensions in the range of 0 dyne s/cm: during cyclic compression. The present review summarizes the availabl e data on the parameters governing lipid-protein interactions of the hydrop hobic surfactant proteins SP-B and SP-C with the main surfactant phospholip ids. Lipid-protein interactions in surfactant have been studied in vitro us ing preparations reconstituted with very different methodological procedure s. Conclusions concerning the role of hydrophobic surfactant Proteins on th e assembly of lipid-protein surfactant structures in vivo have been revised in this respect. This review presents the knowledge available on the dispo sition of SP-B and SP-C in surfactant structures, the mode, extent, selecti vity, and stoichiometry of their lipid-protein interactions, and the effect of the proteins on structure and dynamics of surfactant bilayers and monol ayers. Some considerations are given to possible concerted actions, under p hysiological conditions, of both proteins SP-B and SP-C.