Structures of esterase-like catalytic antibodies

We report structures of complexes of two esterase-like catalytic antibodies elicited against phosphonate transition-state analogues (TSAs) of the reaction they catalyse; the complexes studied are with these TSAs and species along the reaction pathway. The TSAs are deeply sequestered in a pocket located in the combining site at the interface of the two antibody polypeptide chains; the deepest part of this pocket is almost completely hydrophobic. The larger number and stronger hydrogen bonds between the antibodies and the TSAs as compared to those established with the corresponding substrates account for the catalytic activity; transition state stabilisation is through oxyanion holes elicited in response to the negatively charged phosphonate oxygens.