Negative regulation of Bacillus anthracis sporulation by the Spo0E family of phosphatases

The Scripps Research Institute, Department of Molecular and Experimental Medicine, Division of Cellular Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037

^* To whom correspondence should be addressed. Email: mperego{at}scripps.edu.

	Abstract

The initiation of sporulation in Bacillus species is controlled by the phosphorelay signal transduction system. Multiple regulatory elements act on the phosphorelay to modulate the level of protein phosphorylation in response to cellular, environmental and metabolic signals. In Bacillus anthracis nine possible histidine sensor kinases can positively activate the system while two response regulator aspartyl phosphate phosphatases of the Rap family negatively impact the pathway by dephosphorylating the Spo0F intermediate response regulator. In this study, we have characterized the B. anthracis members of the Spo0E family of phosphatases that specifically dephosphorylate the Spo0A response regulator of the phosphorelay and master regulator of sporulation. The products of four genes were able to promote the dephosphorylation of Spo0AP in vitro. The overexpression of two of these B. anthracis Spo0E-like proteins from a multicopy vector consistently resulted in a sporulation deficient phenotype. A third gene was found to be not transcribed in vivo. A fourth gene encoded a prematurely truncated protein due to a base pair deletion that nevertheless was subject to translational frame shift repair in an E. coli protein expression system. A fifth Spo0E-like protein was structurally and functionally characterized as a phosphatase of Spo0AP in Grenha et al. (J. Biol. Chem., 2006, in press). We propose that these proteins may contribute to maintain B. anthracis in the transition phase of growth during an active infection, therefore contributing to the virulence of this organism.