| Abstract: | ["Polar lipids must flip rapidly, and often bi-directionally, across membranes to support cellular life. As flipping is energetically costly, specialized transporters increase its intrinsically low rate to a physiologically relevant level. While some of these transporters couple ATP hydrolysis to lipid movement, many function without any discernible metabolic energy input. The molecular identification of these latter \u2018ATP-independent flippases\u2019, also termed \u2018scramblases\u2019, has eluded researchers for decades - until recently. I will discuss the first examples of this novel class of proteins: afTMEM16, a fungal homolog of the TMEM16 family of ion channels is a Ca2+-dependent phospholipid scramblase [1] and rhodopsin, a prototypical G protein-coupled receptor, is a constitutively active phospholipid scramblase responsible for the homeostasis of photoreceptor disc membranes [2, 3]. \r\n\r\n1. Malvezzi, M. Chalat, M.N., Janjusevic, R., Picollo, A., Terashima, H., Menon, A.K.*, Accardi, A.* (2013) Ca2+-dependent phospholipid scrambling by a reconstituted TMEM16 ion channel. Nature Commun. 4, 2367.\r\n2. Menon, I., Huber, T., Sanyal, S., Banerjee, S., Barr\u00e9, P., Canis, S., Warren, J.D., Hwa, J., Sakmar, T.P., Menon, A.K. (2011) Opsin is a phospholipid flippase. Curr. Biol. 21, 149-153.\r\n3. Goren, M.A., Morizumi, T., Menon, I., Joseph, J.S., Dittman, J.S., Cherezov, V., Stevens, R., Ernst, O.P., Menon, A.K. (2014) Constitutive phospholipid scramblase activity of a G protein-coupled receptor. Nature Commun. 5, 5115"] |
