The type 4 prepilin peptidases comprise a novel family of aspartic acid proteases

Type 4 prepilins or prepilin-like-proteins are secreted by a wide range of bacterial species and are required for a variety of functions including typ e 4 pilus formation, toxin and other enzyme secretion, gene transfer, and b iofilm formation. A distinctive feature of these proteins is the presence o f a specialized leader peptide that is cleaved off by a cognate membrane-bo und type 4 prepilin peptidase (TFPP) during the process of secretion. In th is report we show that the TFPPs represent a novel family of bilobed aspart ate proteases that is unlike any other protease. The active site pairs of a spartic acids of the two TFPPs in Vibrio cholerae are found at positions 12 5 and 189 of TcpJ and 147 and 212 of VcpD. Corresponding aspartate residues are completely conserved throughout this extensive peptidase family.