Aspartyl-phosphate phosphatases deactivate the response regulator components of the sporulation signal transduction system in Bacillus subtilis

Authors

  • Marta Perego,

    1. Department of Molecular and Experimental Medicine, Division of Cellular Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, California 92037, USA.
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  • Philippe Glaser,

    1. Institute Pasteur, Department of Regulation of Genetic Expression, 28 Rue du Dr Roux, 75724 Paris, France.
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    • Sir William Dunn School of Pathology, Chemical Pathology Unit, Oxford University, South Parks Road, Oxford OX2 3RE, UK.

  • James A. Hoch

    Corresponding author
    1. Department of Molecular and Experimental Medicine, Division of Cellular Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, California 92037, USA.
    • For correspondence. E-mail hoch@scripps.edu; Tel. (619) 784 7905; Fax (619) 784 7966.

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Summary

Bacteria use two-component signal transduction systems to sense and respond to their environment. A sensor kinase and a response-regulator transcription factor work in concert by phosphorylation/dephosphorylation through kinase and phosphatase activities to maintain a level of phosphorylated response regulator commensurate with the level of signal input. Signal input can be accommodated through stimulation of the kinase activity or the phosphatase activity of the two-component system. With some notable exceptions, the sensor kinases recognize a single stimulatory ligand. A new dimension in the regulation of two-component signal transduction systems was discovered in the Rap phosphatases which dephosphorylate the Spo0F response-regulator of Bacillus subtilis independent of the sensor kinases. This family of phosphatases is encoded by at least six chromosomal genes. Although not all of the phosphatases of the family have activity on phosphorylated Spo0F, the two best-characterized members, RapA and RapB, prevent sporulation by dephosphorylating this response regulator component of the phosphorelay. Phosphatase activity of RapA is regulated by a gene, phrA, in the same transcriptional unit, that encodes a peptide secreted from the cell which may serve as a quorum sensor. Most of the Rap phosphatase operons have a gene coding for a protein with some similarity to PhrA in their transcription units, but it is uncertain whether all of these play a role in regulation. The Rap phosphatases are postulated to be a mechanism for allowing signals other than those that affect the sensor kinases to regulate the signal transduction pathway. They may have been recruited to help regulate sporulation because the multiple signals regulating this process may out-strip the recognition capacity of the kinases.

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