On the molecular mechanism of flippase- and scramblase-mediated phospholipid transport

Biochim Biophys Acta. 2016 Aug;1861(8 Pt B):767-783. doi: 10.1016/j.bbalip.2015.12.020. Epub 2015 Dec 31.


Phospholipid flippases are key regulators of transbilayer lipid asymmetry in eukaryotic cell membranes, critical to many trafficking and signaling pathways. P4-ATPases, in particular, are responsible for the uphill transport of phospholipids from the exoplasmic to the cytosolic leaflet of the plasma membrane, as well as membranes of the late secretory/endocytic pathways, thereby establishing transbilayer asymmetry. Recent studies combining cell biology and biochemical approaches have improved our understanding of the path taken by lipids through P4-ATPases. Additionally, identification of several protein families catalyzing phospholipid 'scrambling', i.e. disruption of phospholipid asymmetry through energy-independent bi-directional phospholipid transport, as well as the recent report of the structure of such a scramblase, opens the way to a deeper characterization of their mechanism of action. Here, we discuss the molecular nature of the mechanism by which lipids may 'flip' across membranes, with an emphasis on active lipid transport catalyzed by P4-ATPases. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.

Keywords: Cdc50 proteins; Molecular mechanism; P4-ATPases; Regulation; Scramblases; Transbilayer lipid transport.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphatases / physiology*
  • Amino Acid Sequence
  • Animals
  • Biological Transport / genetics
  • Biological Transport, Active / genetics
  • Cell Membrane / metabolism
  • Humans
  • Lipid Bilayers / chemistry
  • Lipid Bilayers / metabolism
  • Membrane Lipids / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Phospholipid Transfer Proteins / physiology*
  • Phospholipids / metabolism*


  • Lipid Bilayers
  • Membrane Lipids
  • Phospholipid Transfer Proteins
  • Phospholipids
  • Adenosine Triphosphatases