Title

Agrobacterium ParA/MinD-like VirC1 spatially coordinates early conjugative DNA transfer reactions.

Publication Date

5-16-2007

Journal

EMBO J. 2007 May 16; 26(10): 2540–2551.

Abstract

Agrobacterium tumefaciens translocates T-DNA through a polar VirB/D4 type IV secretion (T4S) system. VirC1, a factor required for efficient T-DNA transfer, bears a deviant Walker A and other sequence motifs characteristic of ParA and MinD ATPases. Here, we show that VirC1 promotes conjugative T-DNA transfer by stimulating generation of multiple copies per cell of the T-DNA substrate (T-complex) through pairwise interactions with the processing factors VirD2 relaxase, VirC2, and VirD1. VirC1 also associates with the polar membrane and recruits T-complexes to cell poles, the site of VirB/D4 T4S machine assembly. VirC1 Walker A mutations abrogate T-complex generation and polar recruitment, whereas the native protein recruits T-complexes to cell poles independently of other polar processing factors (VirC2, VirD1) or T4S components (VirD4 substrate receptor, VirB channel subunits). We propose that A. tumefaciens has appropriated a progenitor ParA/MinD-like ATPase to promote conjugative DNA transfer by: (i) nucleating relaxosome assembly at oriT-like T-DNA border sequences and (ii) spatially positioning the transfer intermediate at the cell pole to coordinate substrate-T4S channel docking.

Keywords

Adenosine Triphosphatases, Amino Acid Motifs, Amino Acid Sequence, Conjugation, Genetic, DNA, Bacterial, Escherichia coli, Glutathione Transferase, In Situ Hybridization, Fluorescence, Plasmids, Recombinant Proteins, Rhizobium radiobacter, Virulence Factors