Bacteria must withstand large mechanical shear forces when adhering to and colonizing
hosts. Recent structural studies on a class of Gram-positive bacterial adhesins have
revealed an intramolecular Cys-Gln thioester bond that can react with surface-associated
ligands to covalently anchor to host surfaces. Two other examples of such internal thioester
bonds occur in certain anti-proteases and in the immune complement system, both of which
react with the ligand only after the thioester bond is exposed by a proteolytic cleavage. We …