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Succinate-acetate permease from Citrobacter koseri is an anion channel that unidirectionally translocates acetate

Cell Researchvolume 28pages644654 (2018) | Download Citation


Acetate is an important metabolite in metabolism and cell signaling. Succinate-Acetate Permease (SatP) superfamily proteins are known to be responsible for acetate transport across membranes, but the nature of this transport remains unknown. Here, we show that the SatP homolog from Citrobacter koseri (SatP_Ck) is an anion channel that can unidirectionally translocate acetate at rates of the order of ~107 ions/s. Crystal structures of SatP_Ck in complex with multiple acetates at 1.8 Å reveal that the acetate pathway consists of four acetate-binding sites aligned in a single file that are interrupted by three hydrophobic constrictions. The bound acetates at the four sites are each orientated differently. The acetate at the cytoplasmic vestibule is partially dehydrated, whereas those in the main pore body are fully dehydrated. Aromatic residues within the substrate pathway may coordinate translocation of acetates via anion-π interactions. SatP_Ck reveals a new type of selective anion channel and provides a structural and functional template for understanding organic anion transport.

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The synchrotron radiation experiments were performed at BL41XU of the Spring-8 facility with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (proposal numbers 2015B1933, 2014B1158, 2015A1100, 2015B2100, 2016A2531, 2016B2531, and 2017A2559), and beamlines BL17U1, BL18U1, and BL19U1 of the Shanghai Synchrotron Radiation Facility (SSRF). This work was supported by the Ministry of Science and Technology of China (2017YFA0504800), the National Science and Technology Major Projects for “Major New Drugs Innovation and Development” (2018ZX09711003-003-003), the National Key Scientific Instrument and Equipment Development Program (2012YQ03026010), and the Joint Fund of the National Natural Science Foundation of China and the Israel Science Foundation Research Program (8146114802). B.X. was supported by the China Post-Doctoral Science Foundation (2016M600344). We also thank the Shanghai Municipal Government and ShanghaiTech University for financial support.

Authors contributions:

B.Q. cloned constructs for structure determination, purified proteins, and crystallized SatP_Ck. B.Q. and J.L. collected and analyzed diffraction data, solved the crystal structures, and built and refined atomic models. F.W. and Z.M. participated in crystal optimization. K.H. participated in diffraction data collection. B.Q., Y.L., M.H., F.Z., and L.G. performed mutagenesis. B.X., Q.M., and G.Z. performed channel recordings and analysis. Q.Z. and S.Z. did bioinformatics analysis. J.L. and Z.G. wrote the manuscript with inputs from all authors.

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Author notes

  1. These authors contributed equally: Biao Qiu, Bingqing Xia.


  1. School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China

    • Biao Qiu
    • , Yan Lu
    • , Miaomiao He
    • , Suwen Zhao
    •  & Jun Liao
  2. Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China

    • Biao Qiu
    • , Yan Lu
    • , Miaomiao He
    •  & Jun Liao
  3. CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China

    • Bingqing Xia
    • , Qionglei Mao
    •  & Zhaobing Gao
  4. iHuman Institute, ShanghaiTech University, Shanghai, 201210, China

    • Qingtong Zhou
    •  & Suwen Zhao
  5. Protein Crystal Analysis Division, Japan Synchrotron Radiation Research Institute, Hyogo, 679-5198, Japan

    • Kazuya Hasegawa
  6. Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, Guangdong, 510640, China

    • Zhiqiang Ma
  7. State Key Laboratory of Microbial Technology, Shandong University, Jinan, Shandong, 250100, China

    • Fengyu Zhang
    •  & Lichuan Gu
  8. Wuxi Biortus Biosciences Co., Ltd, Wuxi, Jiangsu, 214437, China

    • Feng Wang
  9. University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China

    • Bingqing Xia
    •  & Qionglei Mao


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The authors declare no competing financial interests.

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Correspondence to Zhaobing Gao or Jun Liao.

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