Ly. Chen et al., Crystal structure of the stromelysin catalytic domain at 2.0 angstrom resolution: Inhibitor-induced conformational changes, J MOL BIOL, 293(3), 1999, pp. 545-557
Matrix metalloproteinases are believed to play an important role in patholo
gical conditions such as osteoarthritis, rheumatoid arthritis and tumor inv
asion. Stromelysin is a zinc-dependent proteinase and a member of the matri
x metalloproteinase family. We have solved the crystal structure of an acti
ve uninhibited form of truncated stromelysin and a complex with a hydroxama
te-based inhibitor. The catalytic domain of the enzyme of residues 83-255 i
s an active fragment. Two crystallographically independent molecules, A and
B, associate as a dimer in the crystals. There are three alpha-helices and
one twisted, five-strand beta-sheet in each molecule, as well as one catal
ytic Zn, one structural Zn and three structural Ca ions. The active site: o
f stromelysin is located in a large, hydrophobic cleft. Ln particular, the
S1' specificity site is a deep and highly hydrophobic cavity. The structure
of a hydroxamate-phosphinamide-type inhibitor-bound stromelysin complex, f
ormed by diffusion soaking, has been solved as part of our-structure-based
design strategy. The most important feature we observed is an inhibitor-ind
uced conformational change in the S1' cavity which is triggered by Tyr223.
Ln the uninhibited enzyme structure, Tyr223 completely covers the S1' cavit
y, while in the complex, the P1' group of the inhibitor displaces the Tyr22
3 in order to fit into the S1' cavity. Furthermore, the displacement of Tyr
223 induces a major conformational change: of the entire loop from residue
222 to residue 231. This finding provides direct evidence that Tyr223 plays
the role of gatekeeper of the S1' cavity. Another important intermolecular
interaction occurs at the active sit of molecule A, in which the C-termina
l tail (residues 251-255) from molecule B inserts. The C-terminal tail inte
racts extensively with the active site of molecule A, and the last residue
(Thr255) coordinated to the catalytic zinc as the fourth ligand, much like
a product inhibitor would. The inhibitor-induced conformational change and
the intermolecular C-terminal-zinc coordination are significant in understa
nding the structure-activity relationships of the enzyme. (C) 1999 Academic
Press.