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Journal of Bacteriology, February 2009, p. 687-692, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01184-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Unique GTP-Dependent Sporulation Sensor Histidine Kinase in Bacillus anthracis{triangledown} ,{dagger}

Francesca Scaramozzino, Andrea White, Marta Perego, and James A. Hoch*

Division of Cellular Biology, Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 N. Torrey Pines Rd., MEM-116, La Jolla, California 92037

Received 22 August 2008/ Accepted 6 October 2008

The Bacillus anthracis BA2291 gene codes for a sensor histidine kinase involved in the induction of sporulation. Genes for orthologs of the sensor domain of the BA2291 kinase exist in virulence plasmids in this organism, and these proteins, when expressed, inhibit sporulation by converting BA2291 to an apparent phosphatase of the sporulation phosphorelay. Evidence suggests that the sensor domains inhibit BA2291 by titrating its activating signal ligand. Studies with purified BA2291 revealed that this kinase is uniquely specific for GTP in the forward reaction and GDP in the reverse reaction. The G1 motif of BA2291 is highly modified from ATP-specific histidine kinases, and modeling this motif in the structure of the kinase catalytic domain suggested how guanine binds to the region. A mutation in the putative coiled-coil linker between the sensor domain and the catalytic domains was found to decrease the rate of the forward autophosphorylation reaction and not affect the reverse reaction from phosphorylated Spo0F. The results suggest that the activating ligand for BA2291 is a critical signal for sporulation and in a limited concentration in the cell. Decreasing the response to it either by slowing the forward reaction through mutation or by titration of the ligand by expressing the plasmid-encoded sensor domains switches BA2291 from an inducer to an inhibitor of the phosphorelay and sporulation.

* Corresponding author. Mailing address: Division of Cellular Biology, Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037. Phone: (858) 784-7905. Fax: (858) 784-7966. E-mail: hoch{at}scripps.edu

{triangledown} Published ahead of print on 17 October 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, February 2009, p. 687-692, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01184-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

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A Unique Sensor Histidine Kinase
Yih-Ling Tzeng
JB 2009 191: 681-682. [Full Text]  





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