Production and structural studies of lung surfactant protein B (SP-B) peptides

Abstract

Lung surfactant is a mixture of lipids and proteins which is critical for normal breathing by lining the air-water interface to reduce the surface tension. Lung surfactant protein B (SP-B) is the only essential protein component of lung surfactant complex due to the lethality of any SP-B deficiency. It is thought that SP-B functions by enhancing lipid rearrangements at various phases of the breathing cycle. However, the high-resolution structure and mechanism of SP-B are not yet understood. In the first part of this research, SP-B and a 7-residue deletion mutant of SP-B were produced recombinantly and partially characterized. In the second part of this research, circular dichroism, solution and solid-state nuclear magnetic resonance (NMR) methods were used to assess the structure of two SP-B-based peptides, Super-Mini-B and N-terminal insertion sequence (SP-B₁₋₇). Super-Mini-B is composed of the N-terminal 7-residue insertion sequence and the N-and C-terminal helices of SP-B. Interestingly, it was observed that Super-Mini-B produces greater lipid membrane perturbation than the peptide which lacks the N-terminal insertion sequence (i.e. Mini-B). Comparing the results of structural studies on Mini-B, SP-B₁₋₇ and Super-Mini-B helps unveil the contribution of the 7-residue insertion sequence to the function of SP-B.