Role of Agrobacterium VirB11 ATPase in T-pilus assembly and substrate selection

Sagulenko, E., Sagulenko, V., Chen, J. and Christie, P. J. (2001) Role of Agrobacterium VirB11 ATPase in T-pilus assembly and substrate selection. Journal of Bacteriology, 183 20: 5813-5825. doi:10.1128/JB.183.20.5813-5825.2001

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Author Sagulenko, E.
Sagulenko, V.
Chen, J.
Christie, P. J.
Title Role of Agrobacterium VirB11 ATPase in T-pilus assembly and substrate selection
Journal name Journal of Bacteriology   Check publisher's open access policy
ISSN 0021-9193
1098-5530
1067-8832
Publication date 2001-10-01
Sub-type Article (original research)
DOI 10.1128/JB.183.20.5813-5825.2001
Open Access Status File (Publisher version)
Volume 183
Issue 20
Start page 5813
End page 5825
Total pages 13
Place of publication Washington, DC, United States
Publisher American Society for Microbiology
Language eng
Formatted abstract
The VirB11 ATPase is a subunit of the Agrobacterium tumefaciens transfer DNA (T-DNA) transfer system, a type IV secretion pathway required for delivery of T-DNA and effector proteins to plant cells during infection. In this study, we examined the effects of virB11 mutations on VirB protein accumulation, T-pilus production, and substrate translocation. Strains synthesizing VirB11 derivatives with mutations in the nucleoside triphosphate binding site (Walker A motif) accumulated wild-type levels of VirB proteins but failed to produce the T-pilus or export substrates at detectable levels, establishing the importance of nucleoside triphosphate binding or hydrolysis for T-pilus biogenesis. Similar findings were obtained for VirB4, a second ATPase of this transfer system. Analyses of strains expressing virB11 dominant alleles in general showed that T-pilus production is correlated with substrate translocation. Notably, strains expressing dominant alleles previously designated class II (dominant and nonfunctional) neither transferred T-DNA nor elaborated detectable levels of the T-pilus. By contrast, strains expressing most dominant alleles designated class III (dominant and functional) efficiently translocated T-DNA and synthesized abundant levels of T pilus. We did, however, identify four types of virB11 mutations or strain genotypes that selectively disrupted substrate translocation or T-pilus production: (i) virB11/virB11* merodiploid strains expressing all class II and III dominant alleles were strongly suppressed for T-DNA translocation but efficiently mobilized an IncQ plasmid to agrobacterial recipients and also elaborated abundant levels of T pilus; (ii) strains synthesizing two class III mutant proteins, VirB11, V258G and VirB11.I265T, efficiently transferred both DNA substrates but produced low and undetectable levels of T pilus, respectively; (iii) a strain synthesizing the class II mutant protein VirB11. I103T/M301L efficiently exported VirE2 but produced undetectable levels of T pilus; (iv) strains synthesizing three VirB11 derivatives with a four-residue (HMVD) insertion (L75.i4, C168.i4, and L302.i4) neither transferred T-DNA nor produced detectable levels of T pilus but efficiently transferred VirE2 to plants and the IncQ plasmid to agrobacterial recipient cells. Together, our findings support a model in which the VirB11 ATPase contributes at two levels to type IV secretion, T-pilus morphogenesis, and substrate selection. Furthermore, the contributions of VirB11 to machine assembly and substrate transfer can be uncoupled by mutagenesis.
Keyword Agrobacterium tumefaciens
Bacteria
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
 
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Created: Thu, 20 Oct 2011, 10:04:29 EST by Vitaliya Sagulenko on behalf of School of Chemistry & Molecular Biosciences