title: An activation domain of plasmid R1 TraI protein delineates stages of gene transfer initiation.
abstract: Bacterial conjugation is a form of type IV secretion that transports protein and DNA to recipient cells. Specific bacteriophage exploit the conjugative pili and cell envelope spanning protein machinery of these systems to invade bacterial cells. Infection by phage R17 requires F-like pili and coupling protein TraD, which gates the cytoplasmic entrance of the secretion channel. Here we investigate the role of TraD in R17 nucleoprotein uptake and find parallels to secretion mechanisms. The relaxosome of IncFII plasmid R1 is required. A ternary complex of plasmid oriT, TraD and a novel activation domain within the N-terminal 992 residues of TraI contributes a key mechanism involving relaxase-associated properties of TraI, protein interaction and the TraD ATPase. Helicase-associated activities of TraI are dispensable. These findings distinguish for the first time specific protein domains and complexes that process extracellular signals into distinct activation stages in the type IV initiation pathway. The study also provided insights into the evolutionary interplay of phage and the plasmids they exploit. Related plasmid F adapted to R17 independently of TraI. It follows that selection for phage resistance drives not only variation in TraA pilins but diversifies TraD and its binding partners in a plasmid-specific manner.
authors: University of Graz, Institute of Molecular Biosciences, Humboldtstrasse 50, 8010 Graz, Austria.
authors: Silvia
authors: S
authors: Lang
authors: Paul C
authors: PC
authors: Kirchberger
authors: Christian J
authors: CJ
authors: Gruber
authors: Adam
authors: A
authors: Redzej
authors: Sandra
authors: S
authors: Raffl
authors: Guenther
authors: G
authors: Zellnig
authors: Klaus
authors: K
authors: Zangger
authors: Ellen L
authors: EL
authors: Zechner
mesh_terms: D001433:Bacteriolysis; D003227:Conjugation, Genetic; D004265:DNA Helicases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D017909:Levivirus / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D010957:Plasmids / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D018741:Replication Origin; D053586:Virus Internalization
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C064957:traD protein, E coli; C027093:TraI protein, E coli; D004265:DNA Helicases