Polar localization and compartmentalization of ClpP proteases during growth and sporulation in Bacillus subtilis

Spatial control of proteolysis is emerging as a common feature of regulatory networks in bacteria. In the spore-forming bacterium Bacillus subtilis, the peptidase ClpP can associate with any of three ATPases: ClpC, ClpE, and ClpX. Here, we report that ClpCP, ClpEP, and ClpXP localize in foci often near the poles of growing cells and that ClpP and the ATPase are each capable of polar localization independently of the other component. A region of ClpC containing an AAA domain was necessary and sufficient for polar localization. We also report that ClpCP and ClpXP proteases differentially localize to the forespore and mother cell compartments of the sporangium during spore formation. Moreover, model substrates for each protease created by appending recognition sequences for ClpCP or ClpXP to the green fluorescent protein were preferentially eliminated from the forespore or the mother cell, respectively. Biased accumulation of ClpCP in the forespore may contribute to the cell-specific activation of the transcription factor sigma(F) by preferential ClpCP-dependent degradation of the anti-sigma(F) factor SpoIIAB.