The Col-1 Module of Human Matrix Metalloproteinase-2 (MMP-2): Structural/Functional Relatedness between Gelatin-Binding Fibronectin Type II Modules and Lysine-Binding Kringle Domains

Human matrix metalloproteinase-2 (MMP-2) contains three intandem fibronectin type II (FII) repeats that bind gelatin. Here, we report the NMR solution structure of the first FII module of MMP-2 (col-1). The latter is described as a characteristic, globular FII fold containing two βsheets, a stretch of 3[1]helix, a turn of αhelix, and an exposed hydrophobic surface lined with aromatic residues. We show that col-1 binds (ProProGly)6, a mimic of gelatin, with a Ka of approx. 0.42 per mM, and that its binding site involves a number of aromatic residues as well as Arg34, as previously found for the second and third homologous repeats. Moreover, the affinity of the intandem col-1+2 construct (col-12) toward the longer ligand (ProProGly)12 is twice that for (ProProGly)6, as expected from mass action. A detailed structural comparison between FII and kringle domains indicates that four main conformational features are shared: two antiparallel βsheets, a central 3[1]helix, and the quasiperpendicular orientation of the two proximal CysCys bonds. Structure superposition by optimizing overlap of cystine bridge areas results in close juxtaposition of their main βsheets and 3[1]helices, and reveals that the gelatin binding site of FII modules falls at similar locations and exhibits almost identical topological features to those of the lysine binding site of kringle domains. Thus, despite the minor (