Abstract
Trimeric autotransporter adhesins (TAAs) are important virulence factors in Gram-negative pathogens. Despite the variety of hosts ranging from plants to mammals and the specialized regulation of TAAs, their molecular organization follows surprisingly simple rules: they form trimeric surface structures with a head–stalk–anchor architecture. The head and stalk are composed of a small set of domains, building blocks that are frequently arranged repetitively. We propose that this repetitive arrangement facilitates recombination of domains to modulate the specificity of the common function: adhesion to the host.