title: A subset of annular lipids is linked to the flippase activity of an ABC transporter.
abstract: Lipids are critical components of membranes that could affect the properties of membrane proteins, yet the precise compositions of lipids surrounding membrane-embedded protein complexes is often difficult to discern. Here we report that, for the heterodimeric ABC transporter TmrAB, the extent of delipidation can be controlled by timed exposure to detergent. We subsequently characterize the cohort of endogenous lipids that are extracted in contact with the membrane protein complex, and show that with prolonged delipidation the number of neutral lipids is reduced in favour of their negatively charged counterparts. We show that lipid A is retained by the transporter and that the extent of its binding decreases during the catalytic cycle, implying that lipid A release is linked to adenosine tri-phosphate hydrolysis. Together, these results enable us to propose that a subset of annular lipids is invariant in composition, with negatively charged lipids binding tightly to TmrAB, and imply a role for this exporter in glycolipid translocation.
authors.affiliation: Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK.
authors.forename: Chérine
authors.initials: C
authors.lastname: Bechara
authors.affiliation: Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt 60438, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Nöll
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Frankfurt 60438, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Morgner
authors.affiliation: Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK.
authors.forename: Matteo T
authors.identifier: 000000034672471X
authors.initials: MT
authors.lastname: Degiacomi
authors.affiliation: 1] Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt 60438, Germany [2] Cluster of Excellence-Macromolecular Complexes, Goethe-University Frankfurt, Frankfurt 60438, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Tampé
authors.affiliation: Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK.
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry*; D001665:Binding Sites; D019281:Dimerization; D004798:Enzymes / Q000737:chemistry*; D005740:Gases; D008055:Lipids / Q000737:chemistry* / Q000145:classification; D013058:Mass Spectrometry; D010715:Phosphatidylglycerols / Q000737:chemistry
chemical_list: D018528:ATP-Binding Cassette Transporters; D004798:Enzymes; D005740:Gases; D008055:Lipids; D010715:Phosphatidylglycerols