title: Peptidoglycan-binding protein TsaP functions in surface assembly of type IV pili.
abstract: Type IV pili (T4P) are ubiquitous and versatile bacterial cell surface structures involved in adhesion to host cells, biofilm formation, motility, and DNA uptake. In Gram-negative bacteria, T4P pass the outer membrane (OM) through the large, oligomeric, ring-shaped secretin complex. In the β-proteobacterium Neisseria gonorrhoeae, the native PilQ secretin ring embedded in OM sheets is surrounded by an additional peripheral structure, consisting of a peripheral ring and seven extending spikes. To unravel proteins important for formation of this additional structure, we identified proteins that are present with PilQ in the OM. One such protein, which we name T4P secretin-associated protein (TsaP), was identified as a phylogenetically widely conserved component of the secretin complex that co-occurs with genes for T4P in Gram-negative bacteria. TsaP contains an N-terminal carbohydrate-binding lysin motif (LysM) domain and a C-terminal domain of unknown function. In N. gonorrhoeae, lack of TsaP results in the formation of membrane protrusions containing multiple T4P, concomitant with reduced formation of surface-exposed T4P. Lack of TsaP did not affect the oligomeric state of PilQ, but resulted in loss of the peripheral structure around the PilQ secretin. TsaP binds peptidoglycan and associates strongly with the OM in a PilQ-dependent manner. In the δ-proteobacterium Myxococcus xanthus, TsaP is also important for surface assembly of T4P, and it accumulates and localizes in a PilQ-dependent manner to the cell poles. Our results show that TsaP is a novel protein associated with T4P function and suggest that TsaP functions to anchor the secretin complex to the peptidoglycan.
authors.affiliation: Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Siewering
authors.forename: Samta
authors.initials: S
authors.lastname: Jain
authors.forename: Carmen
authors.initials: C
authors.lastname: Friedrich
authors.forename: Mariam T
authors.initials: MT
authors.lastname: Webber-Birungi
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Semchonok
authors.forename: Ina
authors.initials: I
authors.lastname: Binzen
authors.forename: Alexander
authors.initials: A
authors.lastname: Wagner
authors.forename: Stuart
authors.initials: S
authors.lastname: Huntley
authors.forename: Jörg
authors.initials: J
authors.lastname: Kahnt
authors.forename: Andreas
authors.initials: A
authors.lastname: Klingl
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.forename: Lotte
authors.initials: L
authors.lastname: Søgaard-Andersen
authors.forename: Chris
authors.initials: C
authors.lastname: van der Does
mesh_terms: D015153:Blotting, Western; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D036781:Fimbriae Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D009344:Neisseria gonorrhoeae / Q000235:genetics / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D008074:Lipoproteins; D010457:Peptidoglycan; C084295:pilQ protein, bacteria; D036781:Fimbriae Proteins