Nonflagellar appendages and secretion systems of P. carbinolicus. The duplicate geopilins may assemble into the same pilus or different pili. Five minor pilins that assist in geopilin assembly may be incorporated into the pilus at intervals. The Msh pilus has one major pilin and five minor pilins. The Pih pilus has its own putative peptidase, PihH instead of PilD, three large minor pilins, and a major pilin without the motif cleaved by PilD (GFXXXE followed by a hydrophobic segment). Two type II Pul secretion systems may contain two or three pseudopilins each. The Flp pilus has its own putative peptidase, TadV, two major pilins and one minor pilin. The sigma-fimbria pilin CsuE is shorter than its orthologs, so the structural unit may be a heterodimer of CsuE and CsuF. The sigma-fimbria fibrillum may contain both adhesins together or one at a time. The type VI secretion system may incorporate both syringe proteins at once or one at a time.
Aklujkar et al. BMC Genomics 2012 13:690 doi:10.1186/1471-2164-13-690