title: Plant transformation by Agrobacterium tumefaciens: modulation of single-stranded DNA-VirE2 complex assembly by VirE1.
abstract: Agrobacterium tumefaciens infects plant cells by the transfer of DNA. A key factor in this process is the bacterial virulence protein VirE2, which associates stoichiometrically with the transported single-stranded (ss) DNA molecule (T-strand). As observed in vitro by transmission electron microscopy, VirE2-ssDNA readily forms an extended helical complex with a structure well suited to the tasks of DNA protection and nuclear import. Here we have elucidated the role of the specific molecular chaperone VirE1 in regulating VireE2-VirE2 and VirE2-ssDNA interactions. VirE2 alone formed functional filamentous aggregates capable of ssDNA binding. In contrast, co-expression with VirE1 yielded monodisperse VirE1-VirE2 complexes. Cooperative binding of VirE2 to ssDNA released VirE1, resulting in a controlled formation mechanism for the helical complex that is further promoted by macromolecular crowding. Based on this in vitro evidence, we suggest that the constrained volume of the VirB channel provides a natural site for the exchange of VirE2 binding from VirE1 to the T-strand.
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Daphna
authors.initials: D
authors.lastname: Frenkiel-Krispin
authors.forename: Sharon Grayer
authors.initials: SG
authors.lastname: Wolf
authors.forename: Shira
authors.initials: S
authors.lastname: Albeck
authors.forename: Tamar
authors.initials: T
authors.lastname: Unger
authors.forename: Yoav
authors.initials: Y
authors.lastname: Peleg
authors.forename: Jossef
authors.initials: J
authors.lastname: Jacobovitch
authors.forename: Yigal
authors.initials: Y
authors.lastname: Michael
authors.forename: Shirley
authors.initials: S
authors.lastname: Daube
authors.forename: Michal
authors.initials: M
authors.lastname: Sharon
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Deborah
authors.initials: D
authors.lastname: Fass
authors.forename: Tzvi
authors.initials: T
authors.lastname: Tzfira
authors.forename: Michael
authors.initials: M
authors.lastname: Elbaum
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism / Q000648:ultrastructure; D007473:Ion Channels / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism / Q000648:ultrastructure; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000235:genetics* / Q000382:microbiology*; D011485:Protein Binding / Q000235:genetics; D011489:Protein Denaturation / Q000235:genetics; D017433:Protein Structure, Secondary / Q000235:genetics; D014170:Transformation, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D007473:Ion Channels; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; C051582:virE1 protein, Agrobacterium tumefaciens; C051583:virE2 protein, Agrobacterium