Phosphatidylethanolamine has an essential role in Saccharomyces cerevisiae that is independent of its ability to form hexagonal phase structures.
Storey MK, Clay KL, Kutateladze T, Murphy RC, Overduin M, Voelker DR. Phosphatidylethanolamine has an essential role in Saccharomyces cerevisiae that is independent of its ability to form hexagonal phase structures. J Biol Chem. 2001 Dec 21; 276(51):48539-48.