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Substrate selectivity of Lysophospholipid Transporter LplT Involved in Membrane Phospholipid Remodeling in Escherichia coli
Author(s) -
Lin Yibin,
Bogdanov Mikhail,
Tong Shuilong,
Guan Ziqiang,
Zheng Lei
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.661.1
Subject(s) - cardiolipin , biochemistry , cardiolipins , phospholipid , chemistry , acyltransferase , acylation , atp binding cassette transporter , transporter , inner membrane , flippase , substrate (aquarium) , membrane , biology , enzyme , gene , ecology , catalysis , phosphatidylserine
Lysophospholipid transporter (LplT) was previously found to be primarily involved in 2‐ acyl lyso‐PE recycling in gram‐negative bacterium. This work identified the potent role of LplT in maintaining membrane stability and integrity in E.coli envelope. We demonstrated the involvement of LplT in the recycling of three major bacterial phospholipids by using combination of in vitro lysophospholipid binding assay with purified protein and transport assays with E.coli spheroplasts. Our results showed that lyso‐PE and lyso‐PG, but not lyso‐PC, were taken up by LplT for reacylation by acyltransferase/acylACP synthetase (Aas) on the inner leaflet of the membrane. We also found a novel cardiolipin hydrolysis reaction by phospholipase A2 to form diacylated cardiolipin and eventually the completely deacylated head group. These two distinct cardiolipin derivatives were both translocated with comparable efficiency to generate tri‐acylated cardiolipin by Aas, demonstrating the first evidence of cardiolipin remodeling in bacterium and supporting a notion that fatty acid chain is not required for LplT transport. We also found that LplT cannot transport lyso‐PA and its substrate binding was not inhibited by either orthophosphate or glycerol‐3‐ phosphate, revealing that glycerol or ethanolamine head group is the chemical determinant for substrate recognition. Any diacyl form of PE, PG or tetra‐acylated form of cardiolipin could not serve as competitive inhibitors in vitro. Based on an evolutionary structural model, a proposed “sideways sliding” mechanism explains how a conserved membrane‐embedded α‐helical interface excludes diacylphospholipids from the LplT binding site to facilitate efficient flipping of lysophosholipid across the cell membrane. Support or Funding Information This work was supported by NIH grant R01 to Lei Zheng.