title: Calcium-Driven Folding of RTX Domain β-Rolls Ratchets Translocation of RTX Proteins through Type I Secretion Ducts.
abstract: Calcium-binding RTX proteins are equipped with C-terminal secretion signals and translocate from the Ca(2+)-depleted cytosol of Gram-negative bacteria directly into the Ca(2+)-rich external milieu, passing through the "channel-tunnel" ducts of type I secretion systems (T1SSs). Using Bordetella pertussis adenylate cyclase toxin, we solved the structure of an essential C-terminal assembly that caps the RTX domains of RTX family leukotoxins. This is shown to scaffold directional Ca(2+)-dependent folding of the carboxy-proximal RTX repeat blocks into β-rolls. The resulting intramolecular Brownian ratchets then prevent backsliding of translocating RTX proteins in the T1SS conduits and thereby accelerate excretion of very large RTX leukotoxins from bacterial cells by a vectorial "push-ratchet" mechanism. Successive Ca(2+)-dependent and cosecretional acquisition of a functional RTX toxin structure in the course of T1SS-mediated translocation, through RTX domain folding from the C-terminal cap toward the N terminus, sets a paradigm that opens for design of virulence inhibitors of major pathogens.
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Bumba
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Jiri
authors.initials: J
authors.lastname: Masin
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Macek
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Wald
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic; Faculty of Science, Charles University in Prague, Vinicna 5, 128 44 Prague, Czech Republic.
authors.forename: Lucia
authors.initials: L
authors.lastname: Motlova
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Ilona
authors.initials: I
authors.lastname: Bibova
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Nela
authors.initials: N
authors.lastname: Klimova
authors.affiliation: Institute of Organic Chemistry and Biochemistry, ASCR, v.v.i., Flemingovo nam. 2, 16610 Prague, Czech Republic.
authors.forename: Lucie
authors.initials: L
authors.lastname: Bednarova
authors.affiliation: Institute of Organic Chemistry and Biochemistry, ASCR, v.v.i., Flemingovo nam. 2, 16610 Prague, Czech Republic.
authors.forename: Vaclav
authors.initials: V
authors.lastname: Veverka
authors.affiliation: Hamburg Outstation, European Molecular Biology Laboratory, c/o DESY, Notkestrasse 85, D-22607 Hamburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kachala
authors.affiliation: Hamburg Outstation, European Molecular Biology Laboratory, c/o DESY, Notkestrasse 85, D-22607 Hamburg, Germany.
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.affiliation: Institute of Biotechnology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic.
authors.forename: Cyril
authors.initials: C
authors.lastname: Barinka
authors.affiliation: Institute of Microbiology, ASCR, v.v.i., Videnska 1083, 14220 Prague, Czech Republic. Electronic address: sebo@biomed.cas.cz.
authors.forename: Peter
authors.initials: P
authors.lastname: Sebo
mesh_terms: D037361:Adenylate Cyclase Toxin / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism*; D001886:Bordetella pertussis / Q000737:chemistry / Q000201:enzymology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D017510:Protein Folding; D017433:Protein Structure, Secondary; D021381:Protein Transport; D000069177:Type I Secretion Systems / Q000378:metabolism*
chemical_list: D037361:Adenylate Cyclase Toxin; D001427:Bacterial Toxins; D000069177:Type I Secretion Systems; D002118:Calcium