Crystal structure of the cyanide-inhibited Xenopus laevis Cu,Zn superoxide dismutase at 98 K.
The crystal structure of cyanide-inhibited X. laevis Cu,Zn superoxide dismutase has been studied and refined based on diffraction data collected at 98 K. The final R-factor for the 27,299 reflections in the 10.0-1.7 A resolution range is 0.170. The cyanide anion, which is a competitive inhibitor expected to mimic the superoxide binding mode, binds directly to the active site copper atom, replacing the coordinated water molecule. Moreover, the anion establishes a strong electrostatic interaction with the guanidinium group of the conserved active site residue Arg141. The coordination sphere of Cu2+ is partly altered with respect to the uninhibited enzyme: a displacement of 0.41 A in subunit A, and 0.27 A in subunit B of the dimeric enzyme is observed for the Cu2+ ions. Only two ligands in the Cu2+ coordination sphere (His46 and His118) are significantly affected by cyanide binding, whereas virtually no rearrangement of the Zn2+ ligands is reported.
Djinovic Carugo
K
K
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
Battistoni
A
A
Carri
M T
MT
Polticelli
F
F
Desideri
A
A
Rotilio
G
G
Coda
A
A
Bolognesi
M
M
D000818:Animals; D001386:Azides / Q000737:chemistry; D001665:Binding Sites; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D003486:Cyanides / Q000737:chemistry*; D008958:Models, Molecular; D011487:Protein Conformation; D013379:Substrate Specificity; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D014982:Xenopus laevis
D001386:Azides; D003486:Cyanides; D013482:Superoxide Dismutase