Structural Studies of Super-Mini-B: Role of the N-Terminal Insertion Sequence of Surfactant Protein B

Abstract

Lung surfactant is a mixture of phospholipids and proteins that is critical for breathing. The hydrophobic surfactant protein B (SP-B) is essential for the function of lung surfactant. Super Mini-B is a 41-residue peptide with internal disulfide bonds that contains the N-terminal 7-residue insertion sequence and the N-and C-terminal helices of SP-B. It has previously been shown to retain the similar activity to full-length SP-B as measured by dynamic compliance and arterial oxygenation in rat studies. Interestingly, Super-Mini-B performs better than peptides which lack the N-terminal insertion sequence (e.g. Mini-B).We have used circular dichroism and solution and solid state NMR to study Super-Mini-B's structure and lipid interactions in various environments, including anionic micelles. Comparison of the results for Mini-B and Super Mini-B help to unveil the contribution of the 7-residue insertion sequence to the function of SP-B.