<p>Recent emergence and dissemination of plasmid-borne <i>tmexCD1-toprJ1</i> tigecycline resistance threatens the efficacy of tigecycline as a “last-resort” defense against bacterial infections. Here, we report two cryo-EM structures of TMexCD1-TOprJ1 alone and in complex with its NMP inhibitor, and both are determined at the resolutions of 2.97 Å and 3.0 Å, respectively. The symmetry of overall architecture explains how the tripartite organization adopts a 3:6:3 protomer stoichiometry (TOprJ1: TMexC1: TMexD1) to assemble an elongated, rod-like pump spanning bacterial double membranes. The periplasmic TMexC1 adaptor bind the trimeric TOprJ1 funnel via a universal “tip-to-tip” contact, and bridges the bottom TMexD1 engine by extensive interactions. A unique form of resting (R) states is observed for TMexD1 trimer. Besides two binding-interfaces of TMexC1 with TOprJ1 and TMexD1, we characterize a substrate/inhibitor-loading cavity. Collectively, these findings constitute molecular bases for assembly and inhibition of transferable TMexCD1-TOprJ1 machinery, and benefit developing next-generation of antimicrobials targeting functional efflux pump.</p>

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Assembly and inhibition of transferable TMexCD1-TOprJ1 efflux pump

  • Yu Shi,
  • Mengyuan Li,
  • Tao Cui,
  • Jianhua Gan,
  • Haomin Huang,
  • Zhi Su,
  • Runshi Yang,
  • Xing Zhang,
  • Huimin Zhang,
  • Yu Feng,
  • Youjun Feng

摘要

Recent emergence and dissemination of plasmid-borne tmexCD1-toprJ1 tigecycline resistance threatens the efficacy of tigecycline as a “last-resort” defense against bacterial infections. Here, we report two cryo-EM structures of TMexCD1-TOprJ1 alone and in complex with its NMP inhibitor, and both are determined at the resolutions of 2.97 Å and 3.0 Å, respectively. The symmetry of overall architecture explains how the tripartite organization adopts a 3:6:3 protomer stoichiometry (TOprJ1: TMexC1: TMexD1) to assemble an elongated, rod-like pump spanning bacterial double membranes. The periplasmic TMexC1 adaptor bind the trimeric TOprJ1 funnel via a universal “tip-to-tip” contact, and bridges the bottom TMexD1 engine by extensive interactions. A unique form of resting (R) states is observed for TMexD1 trimer. Besides two binding-interfaces of TMexC1 with TOprJ1 and TMexD1, we characterize a substrate/inhibitor-loading cavity. Collectively, these findings constitute molecular bases for assembly and inhibition of transferable TMexCD1-TOprJ1 machinery, and benefit developing next-generation of antimicrobials targeting functional efflux pump.