A ribbon diagram of tissue inhibitor of metalloproteinases 1 (TIMP-1) bound to the catalytic domain of matrix metalloproteinase 3 [MMP-3 (ΔC)]. TIMP-1 is shown in green and MMP-3 (ΔC) is shown in light brown. Cystines, Thr2, Val4 and Ser68 in TIMP-1 are indicated: N, blue; O, red; C, grey; and disulfide bonds, yellow. Strands and helices in TIMP-1 are labelled A–J and 1–4, respectively. The catalytic and structural zinc ions are shown in purple, and calcium ions are shown in orange. The image was prepared from the Brookhaven Protein Data Bank entry (1UEA) using the Swiss PDB viewer .