Major component of the type IV pili that are required for social gliding motility through cycles of extension and retraction. Extended pili are composed of thousands of copies of PilA and retract upon binding to extracellular polysaccharides and thereby pull the cell forward. The two-component PilS2/PilR2 is required for proper assembly of T4P and regulation. By the two-component system PilR/PilS component PilR (PubMed:9401034). In the contrary, PilS is a negative regulator of pilA expression. In addition, an increased level of c-di-GMP correlates with reduced transcription of the pilA gene (PubMed:26124238). Expression of pilA seems to be negatively regulated by the accumulation of pilin at a cell end (PubMed:15743959, PubMed:9401034). Deletion mutants show loss of observable pili. Pilin assembly limits pilus production and S motility. This limitation could be linked to the high frequency of reversal of gliding direction observed in M.xanthus. Reversal implies loss of pili at the leading pole of the cell and commissioning of new pili assembly at the other pole. Belongs to the N-Me-Phe pilin family.