This family includes members such as the experimentally characterized PrsW protease from Bacillus subtilis Swiss:P50738. PrsW mediates site-1 cleavage of anti-sigma factor RsiW, and it senses antimicrobial peptides that damage the cell membrane and other agents that cause cell envelope stress. PrsW proteases, CPBP family (type II CAAX Proteases and Bacteriocin Processing enzymes), YhfC intramembrane metalloprotease, and APH-1 are distantly related. They share four predicted core transmembrane segments and possess similar, yet distinct sets of sequence motifs. The first N-terminal motif in PrsW bears the consensus signature of 'EExxK' the second motif 'FxxxE' and the third motif possess a conserved histidine. The fourth motif, 'HxxxB', is shared by the PrsW proteases and the CPBP, APH-1 and the YhfC families. Site-directed mutagenesis indicates that either double point mutation of the two conserved glutamates in the first motif (E75A/E76A), or a single mutation of the conserved histidine in the fourth motif (H175A), are of functional importance.

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