Structural conservation and functional role of TfpY-like proteins in type IV pilus assembly

Type IV pili are surface filaments that enable versatile pathogens, like <i>Pseudomonas aeruginosa</i>, to adhere to and colonize surfaces. Pili are composed of diverse proteins called pilins, which serve as host receptors for phages. <i>P. aeruginosa</i> uses specific accessory proteins to glycosylate pilins to evade phage infection. Here, we show that TfpY is a conserved accessory protein that does not mediate phage defence. Instead, we propose a mechanism where TfpY facilitates efficient pilus assembly and function. A better understanding of TfpY function will provide insight into how its associated pilins have evolved to resist phage infection in the absence of post-translational modification, how some phages overcome this barrier to infection, and how this can guide the design of phage-based therapeutics.