抽象的
肺表面活性剂的结构和功能完整性取决于几种特异性蛋白质。其中两个,SP-A和SP-D是大而水溶性的,而SP-B和SP-C小且非常疏水。SP-A是26kDa多肽链中的18分,含有N-连接的低聚糖。在结构上,它可以表征为胶原蛋白/凝集素杂种。与SP-B一起加上SP-A,用于将分泌的内源性表面活性剂转化为肺泡衬里中的管状髓鞘。它还通过II型细胞调节表面活性剂分泌和表面活性剂脂质的再摄血;这些功能可能是受体介导的。SP-D是39kDa多肽链的12-ME1,是具有与C型凝集素的结构相似性的胶原糖蛋白。SP-A和SP-D都刺激肺泡巨噬细胞。SP-B是79-残基多肽,其含有三种颈内桥。 It exists mainly as a homodimer, which is strongly positively charged and may selectively remove anionic and unsaturated lipid species from the alveolar surface film, thereby increasing surface pressure. SP-C is a mainly alpha-helical, extraordinarily hydrophobic polypeptide containing 35 amino acid residues and covalently linked palmitoyl groups. Its alpha-helical portion is inserted into surfactant lipid bilayers. SP-C accelerates the adsorption of lipid bilayers to an interfacial monolayer. In babies with respiratory distress syndrome, the clinical response to treatment with surfactant containing SP-B and SP-C is much faster than in babies treated with protein-free synthetic surfactant. We speculate that, in the near future, surfactant preparations based on recombinant hydrophobic proteins will be available for clinical use.