title: ClpV recycles VipA/VipB tubules and prevents non-productive tubule formation to ensure efficient type VI protein secretion.
abstract: The multicomponent type VI secretion system (T6SS) mediates the transport of effector proteins by puncturing target membranes. T6SSs are suggested to form a contractile nanomachine, functioning similar to the cell-puncturing device of tailed bacteriophages. The T6SS members VipA/VipB form tubular complexes and are predicted to function in analogy to viral tail sheath proteins by providing the energy for secretion via contraction. The ATPase ClpV disassembles VipA/VipB tubules in vitro, but the physiological relevance of tubule disintegration remained unclear. Here, we show that VipA/VipB tubules localize near-perpendicular to the inner membrane of Vibrio cholerae cells and exhibit repetitive cycles of elongation, contraction and disassembly. VipA/VipB tubules are decorated by ClpV in vivo and become static in ΔclpV cells, indicating that ClpV is required for tubule removal. VipA/VipB tubules mislocalize in ΔclpV cells and exhibit a reduced frequency of tubule elongation, indicating that ClpV also suppresses the spontaneous formation of contracted, non-productive VipA/VipB tubules. ClpV activity is restricted to the contracted state of VipA/VipB, allowing formation of functional elongated tubules at a T6SS assembly. Targeting of an unrelated ATPase to VipA/VipB is sufficient to replace ClpV function in vivo, suggesting that ClpV activity is autonomously regulated by VipA/VipB conformation.
authors.affiliation: Center for Molecular Biology of the University of Heidelberg and German Cancer Research Center, DKFZ-ZMBH Alliance, Universität Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Kapitein
authors.forename: Gabriele
authors.initials: G
authors.lastname: Bönemann
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Pietrosiuk
authors.forename: Fabian
authors.initials: F
authors.lastname: Seyffer
authors.forename: Ingrid
authors.initials: I
authors.lastname: Hausser
authors.forename: Jacomine Krijnse
authors.initials: JK
authors.lastname: Locker
authors.forename: Axel
authors.initials: A
authors.lastname: Mogk
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D015964:Gene Expression Regulation, Bacterial; D021381:Protein Transport; D014734:Vibrio cholerae / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D000251:Adenosine Triphosphatases