JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Zhao, Z.
Right arrow Articles by Christie, P. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Zhao, Z.
Right arrow Articles by Christie, P. J.

Journal of Bacteriology, July 2001, p. 3855-3865, Vol. 183, No. 13
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.13.3855-3865.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Activities of virE1 and the VirE1 Secretion Chaperone in Export of the Multifunctional VirE2 Effector via an Agrobacterium Type IV Secretion Pathway

Zhenming Zhao, Evgeniy Sagulenko, Zhiyong Ding, and Peter J. Christie*

Department of Microbiology and Molecular Genetics, The University of Texas-Houston Medical School, Houston, Texas 77030

Received 23 January 2001/Accepted 6 April 2001

Agrobacterium tumefaciens uses a type IV secretion system to deliver oncogenic nucleoprotein particles and effector proteins, such as the multifunctional VirE2 protein, to plant cells. In this study, we examined the function of virE1 and its product, the VirE1 secretion chaperone, in mediating VirE2 export. A nonpolar virE1 null mutant accumulated low levels of VirE2, and trans expression of virE1 in this mutant only partially restored VirE2 abundance. Deletion of virE1 did not affect transcription but decreased translation of virE2, as shown by analysis of lacZ transcriptional and translational fusions. VirE2 was stable for a prolonged period, more than 6 h, when it was expressed in cis with virE1, and it exhibited half-lives of about 2 h when it was expressed in trans with virE1 and less than 10 min when it was expressed in the absence of virE1, as shown by pulse-chase experiments. VirE1 stabilized VirE2 via an interaction with a domain near the N terminus of VirE2, as shown by analyses of VirE2 truncation and insertion mutants synthesized in A. tumefaciens. VirE1 self-association was demonstrated by using bacteriophage lambda  cI repressor fusion and pull-down assays, and evidence of VirE1 homomultimerization in vivo was obtained by native polyacrylamide gel electrophoresis and gel filtration chromatography. A putative VirE1-VirE2 complex with a molecular mass of about 70 to 80 kDa was detected by gel filtration chromatography of extracts from wild-type cells, whereas higher-order VirE2 complexes or aggregates were detected in extracts from a virE1 mutant. Taken together, our findings show that virE1 contributes in several ways to VirE2 export:(i) virE1 regulates efficient virE2 translation in the context of expression from the native PvirE promoter; (ii) the VirE1 secretion chaperone stabilizes VirE2, most probably via an interaction with an N-terminal domain; and (iii) VirE1 forms a VirE1-VirE2 complex with a predicted 2:1 stoichiometry that inhibits assembly of higher-order VirE2 complexes or aggregates.

* Corresponding author. Mailing address: Department of Microbiology and Molecular Genetics, The University of Texas-Houston Medical School, 6431 Fannin, Houston, TX 77030. Phone: (713) 500-5440. Fax: (713) 500-5499. E-mail: Peter.J.Christie{at}uth.tmc.edu.

Journal of Bacteriology, July 2001, p. 3855-3865, Vol. 183, No. 13
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.13.3855-3865.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 2001 by the American Society for Microbiology. All rights reserved.