Tryptophan-mediated Dimerization of the TssL Transmembrane Anchor Is Required for Type VI Secretion System Activity |
| |
Authors: | Abdelrahim Zoued Jean-Pierre Duneau Eric Durand Alexandre P España Laure Journet Françoise Guerlesquin Eric Cascales |
| |
Institution: | Laboratoire d''Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 31 chemin Joseph Aiguier, 13402, Marseille Cedex 20, France |
| |
Abstract: | The type VI secretion system (T6SS) is a multiprotein complex used by bacteria to deliver effectors into target cells. The T6SS comprises a bacteriophage-like contractile tail structure anchored to the cell envelope by a membrane complex constituted of the TssJ outer-membrane lipoprotein and the TssL and TssM inner-membrane proteins. TssJ establishes contact with the periplasmic domain of TssM whereas the transmembrane segments of TssM and its cytoplasmic domain interact with TssL. TssL protrudes in the cytoplasm but is anchored by a C-terminal transmembrane helix (TMH). Here, we show that TssL TMH dimerization is required for the stability of the protein and for T6SS function. Using the TOXCAT assay and point mutations of the 23 residues of the TssL TMH, we identified Thr194 and Trp199 as necessary for TssL TMH dimerization. NMR hydrogen–deuterium exchange experiments demonstrated the existence of a dimer with the presence of Trp185 and Trp199 at the interface. A structural model based on molecular dynamic simulations shows that TssL TMH dimer formation involves π–π interactions resulting from the packing of the two Trp199 rings at the C-terminus and of the six aromatic rings of Tyr184, Trp185 and Trp188 at the N-terminus of the TMH. |
| |
Keywords: | protein secretion membrane complex transmembrane helix aromatic rings pi–pi interactions T6SS type VI secretion system TMH transmembrane helix EAEC MD molecular dynamic MBP maltose-binding protein GpA glycophorin A NOESY nuclear Overhauser enhancement spectroscopy H–D hydrogen–deuterium AHT anhydrotetracyclin |
本文献已被 ScienceDirect 等数据库收录! |