The gelatin-binding site of human 72 kDa type IV collagenase (gelatinase A)

To identify structures critical for gelatin-binding of 72 kDa type IV collagenase (gelatinase A), fragments of this metalloproteinase have been expressed in Escherichia coli and assayed for their gelatin affinity. Each of the three fibronectin-related type II domains was found to have affinity for gelatin. Fragments containing all three tandem type II domains had significantly stronger affinity than any of the constituent units, indicating that they co-operate to form the high-affinity gelatin-binding site. Competition experiments have also shown that gelatinase A binds more tightly to gelatin than fibronectin and can displace the latter from denatured collagen.