Unique degradation signal for ClpCP in Bacillus subtilis

Regulation of the cell-specific transcription factor sigma(F) in the spore-forming bacterium Bacillus subtilis involves the antisigma factor SpoIIAB. Contributing to the activation of sigma(F) is the degradation of SpoIIAB in a manner that depends on the protease ClpCP. Here we show that the three residues (LCN) located at the extreme C terminus of SpoIIAB are both necessary and sufficient for this degradation. We also report that the use of the LCN extension as a degradation signal for ClpCP is unique to SpoIIAB.