title: Surface plasmon resonance imaging reveals multiple binding modes of Agrobacterium transformation mediator VirE2 to ssDNA.
abstract: VirE2 is the major secreted protein of Agrobacterium tumefaciens in its genetic transformation of plant hosts. It is co-expressed with a small acidic chaperone VirE1, which prevents VirE2 oligomerization. After secretion into the host cell, VirE2 serves functions similar to a viral capsid in protecting the single-stranded transferred DNA en route to the nucleus. Binding of VirE2 to ssDNA is strongly cooperative and depends moreover on protein-protein interactions. In order to isolate the protein-DNA interactions, imaging surface plasmon resonance (SPRi) studies were conducted using surface-immobilized DNA substrates of length comparable to the protein-binding footprint. Binding curves revealed an important influence of substrate rigidity with a notable preference for poly-T sequences and absence of binding to both poly-A and double-stranded DNA fragments. Dissociation at high salt concentration confirmed the electrostatic nature of the interaction. VirE1-VirE2 heterodimers also bound to ssDNA, though by a different mechanism that was insensitive to high salt. Neither VirE2 nor VirE1-VirE2 followed the Langmuir isotherm expected for reversible monomeric binding. The differences reflect the cooperative self-interactions of VirE2 that are suppressed by VirE1.
authors.affiliation: Dept of Materials and Interfaces, Weizmann Institute of Science, 7610001 Rehovot, Israel.
authors.forename: Sanghyun
authors.initials: S
authors.lastname: Kim
authors.affiliation: Dept of Materials and Interfaces, Weizmann Institute of Science, 7610001 Rehovot, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Zbaida
authors.affiliation: Dept of Materials and Interfaces, Weizmann Institute of Science, 7610001 Rehovot, Israel michael.elbaum@weizmann.ac.il.
authors.forename: Michael
authors.initials: M
authors.lastname: Elbaum
authors.affiliation: LBPA, Institut d'Alembert, ENS de Cachan, CNRS, 61, avenue du Président Wilson, F-94235 Cachan, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Leh
authors.affiliation: LBPA, Institut d'Alembert, ENS de Cachan, CNRS, 61, avenue du Président Wilson, F-94235 Cachan, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Nogues
authors.affiliation: LBPA, Institut d'Alembert, ENS de Cachan, CNRS, 61, avenue du Président Wilson, F-94235 Cachan, France buckle@lbpa.ens-cachan.fr.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Buckle
mesh_terms: D016960:Agrobacterium tumefaciens; D001426:Bacterial Proteins / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D009994:Osmolar Concentration; D011485:Protein Binding; D020349:Surface Plasmon Resonance
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D007473:Ion Channels; C051583:virE2 protein, Agrobacterium