The propeptide of human protein from this family has an N-terminal alpha-helical segment whose suggested function was stabilization of the protein structure, since the latter can irreversibly transform from its native alpha-helical structure to beta-sheet aggregates and form amyloid fibrils. The correct intracellular trafficking of proSP-C has also been reported to depend on the propeptide.
^Li J, Liepinsh E, Almlén A, Thyberg J, Curstedt T, Jörnvall H, Johansson J (March 2006). "Structure and influence on stability and activity of the N-terminal propeptide part of lung surfactant protein C". Febs J.273 (5): 926–35. doi:10.1111/j.1742-4658.2006.05124.x. PMID16478467.