Three-dimensional reconstruction of Agrobacterium VirE2 protein with single-stranded DNA

Asmahan Abu-Arish, Daphna Frenkiel-Krispin, Tobin Fricke, Tzvi Tzfira, Vitaly Citovsky, Sharon Grayer Wolf, Michael Elbaum

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

Agrobacterium tumefaciens infects plant cells by a unique mechanism involving an interkingdom genetic transfer. A single-stranded DNA substrate is transported across the two cell walls along with the bacterial virulence proteins VirD2 and VirE2. A single VirD2 molecule covalently binds to the 5′-end of the single-stranded DNA, while the VirE2 protein binds stoichiometrically along the length of the DNA, without sequence specificity. An earlier transmission/scanning transmission electron microscopy study indicated a solenoidal ("telephone coil") organization of the VirE2-DNA complex. Here we report a three-dimensional reconstruction of this complex using electron microscopy and single-particle image-processing methods. We find a hollow helical structure of 15.7-nm outer diameter, with a helical rise of 51.5 nm and 4.25 VirE2 proteins/turn. The inner face of the protein units contains a continuous wall and an inward protruding shelf. These structures appear to accommodate the DNA binding. Such a quaternary arrangement naturally sequesters the DNA from cytoplasmic nucleases and suggests a mechanism for its nuclear import by decoration with host cell factors. Coexisting with the helices, we also found VirE2 tetrameric ring structures. A two-dimensional average of the latter confirms the major features of the three-dimensional reconstruction.

Original languageEnglish
Pages (from-to)25359-25363
Number of pages5
JournalJournal of Biological Chemistry
Volume279
Issue number24
DOIs
StatePublished - 11 Jun 2004
Externally publishedYes

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