The Fibronectin-like Domain Is Required for the Type V and XI Collagenolytic Activity of Gelatinase B

Gelatinase B (matrix metalloproteinase-9) is able to degrade several extracellular matrix proteins, including gelatin, elastin, and collagen types IV, V, XI, and XIV. This enzyme contains a “fibronectin-like” domain which is composed of three tandem copies of a fibronectin type 2 homology unit inserted into its catalytic domain. We have studied the involvement of this domain in the substrate specificity of gelatinase B by expressing a mutant of the enzyme, inEscherichia coli,in which this domain has been deleted. This mutant enzyme retained its ability to cleave the peptide substrate Mca-PLGL(Dpa)AR-NH2, possessingKmandkcatvalues similar to those of the wild-type enzyme. In addition, the NH2-terminal, 14-kDa, inhibitory domain of recombinant tissue inhibitor of metalloproteinase-2 was able to inhibit the mutant and the wild-type enzymes with the same potency. The mutantʹs gelatinolytic activity was also retained but reduced in comparison to that of the wild-type enzyme. However, contrary to the wild-type enzyme, the mutant was not able to digest or bind fibrillar collagen types V and XI. These data indicate that the fibronectin-like domain of gelatinase B is an important determinant of the enzymeʹs fibrillar collagen substrate specificity. It allows the enzyme to bind to and cleave collagen types V and XI, events which are thought to be involved in several normal physiological and pathological processes such as metastasis and arthritis.