Crystallographic study of azide-inhibited bovine Cu,Zn superoxide dismutase.
The crystal structure of azide-inhibited bovine Cu,Zn superoxide dismutase has been studied and refined based on X-ray synchrotron radiation data, in conjunction with difference Fourier and restrained crystallographic refinement techniques. The final R-factor for the 20,756 reflections in the 10.0 to 2.1 A resolution range is 0.166. In both enzyme subunits, the azide anion, which is a competitive inhibitor expected to mimic the superoxide binding mode, is observed directly coordinated to the Cu2+ at the place of the metal-bound water molecule, forming an ion pair with the conserved active site residue Arg141. The coordination sphere of Cu2+ is partly altered with respect to the uninhibited enzyme: a displacement of 0.67 A in subunit A, and 0.37 A in subunit B of the dimeric enzyme is observed for the Cu2+. Only two ligands in the Cu2+ coordination sphere (His46 and His118) are affected by azide binding, whereas virtually no rearrangement of the Zn2+ ligands is reported.
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
K
K
Djinović-Carugo
F
F
Polticelli
A
A
Desideri
G
G
Rotilio
K S
KS
Wilson
M
M
Bolognesi
D000818:Animals; D001386:Azides / Q000494:pharmacology; D002417:Cattle; D018360:Crystallography, X-Ray; D011487:Protein Conformation; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000737:chemistry*
D001386:Azides; D013482:Superoxide Dismutase