X‐ray Structures of Binary and Ternary Enzyme‐Product‐Inhibitor Complexes of Matrix Metalloproteinases

A helicoidal filament results from the approach of the N-terminus of the mutated variant of the catalytic domain of MMP-12 with the catalytic zinc center of another molecule (see X-ray structure); adjacent filaments are arranged in double helices. The N-terminal fragment is proposed to be analogous to an N-terminal polypeptide product after cleavage. Crystals yield two contrasting structures, in which the NH3+ ion is either triply hydrogen bonded, or only exhibits van der Waals interactions.