prepilin

Prepilin is the precursor protein that is processed to form pilin, the subunits that polymerize to construct type IV pili in many bacteria. Prepilins are typically synthesized with an N-terminal class III signal peptide that targets them to the inner membrane.

A dedicated prepilin peptidase, commonly called PilD, cleaves the leader sequence and often catalyzes N-methylation of the newly exposed N-terminus on mature pilin. The mature pilin is then exported and assembled into pili by the type IV pilus assembly machinery.

Prepilins have a short, positively charged leader followed by a hydrophobic region. After processing, the hydrophobic N-terminus becomes part of the mature pilin and contributes to its incorporation into the pilus fiber.

Processing of prepilins is essential for pilus assembly. Type IV pili mediate surface adhesion, twitching motility, DNA uptake during transformation, biofilm formation, and interactions with hosts in some pathogens.

Genetically, pilA encodes the major pilin, while additional prepilins encode minor pilins. These genes are often organized in operons and co-regulated with the pilus assembly machinery.