Bacteria, but also archaea, have evolved a variety of complex surface nanomachines essential for their survival. Among these, the type IV filament is remarkable in that it can support nearly ten distinct cellular functions to date. However, although TFFs are known to extend and retract an extracellular pilin fiber, the general principles governing their functional accessorisation remain poorly defined. Here, we demonstrate at the molecular level that interactions between the motor ATPase and the cytoplasmic platform control the function of three TFF subfamilies: the T4aP, the MSH pili, and the type II secretion system. Furthermore, we show that this interaction can be regulated spatially and temporally by either a protein factor or a small molecule. Ultimately, our work provides molecular insight into the evolutionary routes by which TFFs have become increasingly sophisticated, giving rise to new integrated cellular functions.
