Substrate-translocase interactions during two-partner secretion in Gram-negative bacteria

• Applicant: Professor Dr. Matthias Müller
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2008 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 43311986

• Final Report Year: 2016

Final Report Abstract

Research proposed in project P4 of FOR 929 focused on interactions of protein transporters present in the inner and outer membranes of Gram-negative bacteria and their specific substrate proteins. The twin-arginine translocation (Tat) system of E. coli consists of three membrane proteins (TatA, TatB, TatC) that assemble in order to facilitate translocation of a subset of folded proteins across the inner membrane of E. coli. Using fluorescence labeling we were able to visualize the assembly of TatA, TatB, and TatC in living cells and demonstrate that this process occurs at distinct sites of the inner membrane in strict response to a newly synthesized substrate protein. The type-V secretion pathway secretes virulence factors of pathogenic Gram-negative bacteria across b-barrel-type pore proteins of the outer membrane. We were able to reproduce in vitro two branches of this type-V secretion pathway, the two-partner secretion and the autotransporter pathway. Our results indicate that autotransporters require the b-barrel assembly machinery (BAM complex) for transport and that in vitro integrated b-barrel proteins are functionally active.

Publications

• Early contacts between substrate proteins and TatA translocase component in twin-arginine translocation. J. Biol. Chem. 286, 43679-43689 (2011)
  Fröbel, J., Rose, P. & Müller, M.
  
• Mapping precursor-binding site on TatC subunit of twin-arginine-specific protein translocase by site-specific photo cross-linking. J. Biol. Chem. 287, 13430-13441 (2012)
  Zoufaly, S., Fröbel, J., Rose, P., Flecken, T., Maurer, C., Moser, M. & Müller, M.
  
• Transmembrane insertion of twin-arginine signal peptides is driven by TatC and regulated by TatB. Nat. Commun. 3:1311
  Fröbel, J., Rose, P., Lausberg, F., Blümmel, A.S., Freudl, R & Müller, M.
  
• Twin-arginine-dependent translocation of folded proteins. Phil. Trans. R. Soc. B 367, 1029-1046 (2012)
  Fröbel, J., Rose, P. & Müller, M.
  
• Two-partner secretion of Gram-negative bacteria: A single beta-barrel protein enables transport across the outer membrane. J. Biol. Chem. 287, 2591-2599 (2012)
  Fan, E., Fiedler, S., Jacob-Dubuisson, F. & Müller, M.
  
• Substrate-dependent assembly of the Tat translocase as observed in live Escherichia coli cells. PLoS ONE 8, e69488
  Rose, P., Fröbel, J., Graumann, P.L. & Müller, M.
  
• Versatile in vitro system to study translocation and functional integration of bacterial outer membrane proteins. Nat. Commun. 5:5396
  Norell, D., Heuck, A., Tran-Thi, T.A., Götzke, H. Jacob-Dubuisson, F., Clausen, T., Daley, D.O., Braun, V., Müller, M. & Fan, E.
  
• A single FhaC beta-domain is required for translocation – implications for the role of BamA. Methods Mol. Biol. 1329, 111- 125 (2015)
  Fan, E., Norell, D. & Müller, M.