Type IV prepilin peptidase

International audienceThis chapter covers the structural chemistry and the biological aspects of type IV prepilin peptidase. Type IV prepilin peptidases and type IV prepilin-like peptidases are homologous over their entire amino acid sequences, and in some but not all cases are interchangeable in vivo. Type IV prepilin peptidases are located in the cytoplasmic membrane, but have large, relatively hydrophilic domains in the cytoplasm (domain 1). These cytoplasmic domains are the parts of the proteins that are most highly conserved in the type IV prepilin peptidase family. Because of the inherent difficulties in the purification of integral membrane proteins by conventional methods, the purification of type IV prepilin peptidase from P. aeruginosa is accomplished by detergent solubilization of the membranes and immunoaffinity chromatography. This method remains the method of choice for obtaining type IV prepilin-like peptidase in a pure form. One of the more interesting properties of the type IV prepilin peptidase is its bifunctionality. This protease not only cleaves the leader sequence but also carries out N-terminal methylation of the mature pilin. This peptidase differs from the two other known signal peptidases, LepB, the major signal peptidase, and LspA, the lipoprotein signal peptidase