The propeptide of pulmonary surfactant C has an N-terminal alpha-helical segment whose suggested function was stabilization of the protein structure, since the mature peptide can irreversibly transform from its native alpha-helical structure to beta-sheet aggregates and form amyloid fibrils.
A specific part of the propeptide of pulmonary surfactant C has an N-terminal alpha-helical section that was initially believed to contribute to maintaining the protein's structure, but it actually undergoes a transformation from its native alpha-helix to beta-sheets and amyloid fibers when the protein matures.