Convergent evolution as a mechanism for pathogenic adaptation.

The survival of human pathogens depends on their ability to modulate defence pathways in human host cells. This was thought to be attained mainly by pathogen specific "virulence factors". However, pathogens are increasingly being discovered that use distant homologs of the human regulatory proteins as virulence factors. We analyzed several cases of this approach, with a particular focus on virulence proteases. The analysis reveals clear cases of bacterial proteases mimicking the specificity of their human counterparts, such as strong similarities in their active and/or binding sites. With more sensitive tools for distant homology recognition, we could expect to discover many more such cases.