STRUCTURE AND FUNCTION OF SURFACTANT PROTEIN D

肺的肺泡被一层薄薄的表面活性物质所覆盖

The alveoli of the lung are covered by a thin layer of surface-active material, referred to as pulmonary surfactant. This material, which is essential for normal gas exchange, consists of phospholipids and specific proteins. The best characterized surfactant proteins include SP-A, and two smaller hydrophobic proteins, SP-B and SP-C. We have recently purified a collagenous surfactant-associated glycoprotein from rat lung. This protein, designated SP-D, is different that SP-A and previously described collagenous proteins. Preliminary experiments indicate that SP-D has carbohydrate-binding activity in vitro, and that there is structural homology of SP-D with the C-type (calcium-dependent) lectins. It is our hypothesis that the carbohydrate-binding activity mediates interactions of SP-D with other components of surfactant, and that carbohydrate-mediated interactions contribute to the function of this protein and pulmonary surfactant in vivo. We propose the following specific aims: 1. To further define the structure of SP-D; 2. To characterize its carbohydrate-binding activity; 3. To identify the ligands for SP-D in surfactant; and 4. To explore the possible contributions of SP-D to surfactant activity and metabolism. These studies should contribute important new information relating to the macromolecular composition, organization, and functions of pulmonary surfactant, and to the structure and function of collagenous lectins.