ASTACINS, SERRALYSINS, SNAKE-VENOM AND MATRIX METALLOPROTEINASES EXHIBIT IDENTICAL ZINC-BINDING ENVIRONMENTS (HEXXHXXGXXH AND MET-TURN) ANDTOPOLOGIES AND SHOULD BE GROUPED INTO A COMMON FAMILY, THE METZINCINS

The X-ray crystal structures of two zinc endopeptidases, astacin from crayfish, and adamalysin II from snake venom, reveal a strong overall topological equivalence and virtually identical extended HEXXHXXGXXH z inc-binding segments, but in addition a methionine-containing turn of similar conformation (the 'Met-tum'), which forms a hydrophobic basis for the zinc ion and the three liganding histidine residues. These two features are also present in a similar arrangement in the matrix meta lloproteinases (matrixins) and in the large bacterial Serratia protein ase-like peptidases (serralysins). We suggest that these four proteina ses represent members of distinct subfamilies which can be grouped tog ether in a family, for which we propose the designation, metzincins.