SPECIFIC, HIGH-AFFINITY BINDING OF TISSUE INHIBITOR OF METALLOPROTEINASES-4 (TIMP4) TO THE COOH-TERMINAL HEMOPEXIN-LIKE DOMAIN OF HUMAN GELATINASE-A - TIMP-4 BINDS PROGELATINASE-A AND THE COOH-TERMINAL DOMAIN IN A SIMILAR MANNER TO TIMP-2

The binding properties of the newly described tissue inhibitor of meta lloproteinases-4 (TIMP-4) to progelatinase A and to the COOH-terminal hemopexin-like domain (C domain) of the enzyme were examined. We prese nt evidence for the first time of a specific, high affinity interactio n between TIMP-4 and the C domain of human gelatinase A and show that TIMP-4 binds both progelatinase A and the C domain in a similar manner to that of TIMP-2. Saturable binding of recombinant C domain to TIMP- 4 and to TIMP-2 but not to TIMP-1 was demonstrated using a microwell p rotein binding assay, The recombinant collagen binding domain of gelat inase A, comprised of the three fibronectin type II-like repeats, did not bind to TIMP-4, indicating that binding is mediated selectively by the C domain. Binding to TIMP-4 was of high affinity with an apparent K-d of 1.7 x 10(-7) M but slightly weaker than that to TIMP-2 (appare nt K-d of 0.66 x 10(-7) M). Affinity chromatography confirmed the TIMP -4-C domain interaction and also showed that the complex could not be disrupted by 1 M NaCl or 10% dimethyl sulfoxide, thereby further demon strating the tight binding, To verify the biological significance of t his interaction, binding of full-length progelatinase A to TIMP-4 was investigated. TIMP-4 and TIMP-2 but not TIMP-1 bound specifically to p urified TIMP-2-free human recombinant full-length progelatinase A and to full-length Pat proenzyme from the conditioned culture medium of BO S 17/2.8 cells. Preincubation of the C domain with TIMP-2 was found to reduce subsequent binding to TIMP-4 in a concentration-dependent mann er. Competition between TIMP-2 and TIMP-4 for a common or overlapping binding sites on the gelatinase A C domain may occur; alternatively TI MP-2 may prevent the binding of TIMP-4 by steric hindrance or inductio n of a conformational change in the C domain, We propose that the bind ing of progelatinase A to TIMP-4 represents a third TIMP-progelatinase interaction in addition to that of progelatinase A with TIMP-8 and pr ogelatinase B with TIMP-1 described previously. This new phenomenon ma y be of important physiological significance in modulating the cell su rface activation of progelatinase A.