2.A.1.42.1
The lysophospholipid (LPL) transporter, LplT (Harvat et al., 2005).  Substrates include lyso-PE, lyso-cardiolipin, diacylcardiolipin, fully-deacylated cardiolipin and lyso-phosphatidylglycerol, but not lysophosphatidylcholine, lysophosphatidic acid or phosphatidic acid (Lin et al. 2016). Reacylation by acyltransferase/acyl-acyl carrier protein synthetase then occurs on the inner leaflet of the membrane.Thus, a fatty acid chain is not required for LplT transport. A "sideways sliding" mechanism was proposed to explain how a conserved membrane-embedded α-helical interface excludes diacylphospholipids from the LplT binding site to facilitate efficient flipping of lysophospho-lipids across the cell membrane (Lin et al. 2016). Thus, a fatty acid chain is not required for LplT transport. Fruther, LplT cannot transport lysophosphatidic acid, and its substrate binding was not inhibited by either orthophosphate or glycerol 3-phosphate, indicating that either a glycerol or ethanolamine headgroup is the chemical determinant for substrate recognition. Diacyl forms of PE, phosphatidylglycerol, or the tetra-acylated form of cardiolipin could not serve as competitive inhibitors .A "sideways sliding" mechanism was proposed to explain how a conserved membrane-embedded α-helical interface can exclude diacylphospholipids from the LplT binding site. A dual substrate-accessing mechanism, in which LplT recruits LPLs to its substrate-binding site via two routes, either from its extracellular entry site, or through a membrane-embedded groove between transmembrane helices, and it then moves them towards the inner membrane leaflet (Lin et al. 2018).