3.A.7.18.2
Type IV-like, Tad-like protein secretion system, the Kil system, potentially containing up to 21 proteins. The genes of this system are encoded within two gene clusters, MXAN_3102-3108 and MXAN_4648-4661. All 21 gene products are included within this TC entry although it is not established that all participate in secretion. The descriptions of the proteins are as listed in UNIPROT. Myxococcus xanthus, a soil bacterium, predates collectively using motility to invade prey colonies. Prey lysis is mostly thought to rely on secreted factors, cocktails of antibiotics and enzymes as well as direct contact with Myxococcus cells. Seef et al. 2021 showed that on surfaces, the coupling of A-motility and contact-dependent killing is the central predatory mechanism driving effective prey colony invasion and consumption. At the molecular level, contact-dependent killing involves a type IV filament-like machinery (Kil) that both promotes motility arrest and prey cell plasmolysis. In this process, Kil proteins assemble at the predator-prey contact site, suggesting that they allow tight contact with prey cells for their intoxication. Kil-like systems form a new class of Tad-like machineries in predatory bacteria, suggesting a conserved function in predator-prey interactions. The system allows a novel cell-cell interaction function for bacterial pilus-like assemblages (Seef et al. 2021).